Ground source heat pumps are now being installed in around 97% of new builds in Sweden, I understand.
Here in the UK with a maritime climate we don't even nee to go to that much expense as we can install the far cheaper air source heat pumps as it rarely drops far below zero for long periods.
Needless to say the UK government is providing no encouragement or support, whilst in France they put in 50,000 a year.
A couple of alternative suggestions which may provide a quicker pay-back:
You can now buy heat reclamation coils for your waste from hot water.
They are a copper coil, which feeds cold water around your waste, and returns it to your tank heated.
If it is in a shower that is all you need, as the water comes in and goes out at the same time.
If it is for the washing machine or whatever you will need another tank, as the water does not flow out at the same time.
Another system which may provide better ROI is solar thermal panels.
I would suggest the vacuum evacuated tube type, and to insulate them well, as they provide more hot water on cloudy days than the alternatives.
You can buy some which are designed to be combined at a later date with PV panels- of these amorphous silicon is far better in cloudy weather.
You might also consider buying a few square feet of aerogel at $5/foot, as with it you can insulate those areas that are difficult by traditional means, such as the corners of windowframes.
Triple glazing, standard in Sweden, eliminates condensation problems such as you get with double glazing, as it is almost as good an insulator as the wall around it.
You may instead want to explore solar-heated borehole thermal energy storage, as it has been implemented at this subdivision near Calgary, though your system could be much smaller; http://www.dlsc.ca/how.htm
Solar energy is captured year-round by rooftop solar collectors and stored in the ground by pumping the heated fluid into borehole piping loops
Overview
This system will provide 95% of the heat for these homes near frigid Calgary. Your system would be much smaller, maybe a couple of boreholes and no tanks. Here's an photo of the actual completed community;
That is a nice project, but it requires a new development with district heating. I think that an individual home could to something similar with a ground source heat pump and solar thermal collectors.
During the summer, the hot water is circulated down into the ground heating the soil and storing the energy. During the winter months, when it is cloudy and you can not use solar thermal heating, you can draw from the heat stored in the ground to heat the home using the heat pump.
Even without solar collectors, ground-source heat pumps store and reuse energy. When cooling the house for the summer, heat is rejected to the ground. When winter comes, that heat can be extracted from the ground to heat the house. As spring approaches, the ground has been cooled after the witner and is thus is a more efficient medium for cooling the house.
Yes, however many places in the U.S. do not require much AC in the summer but require a lot of heating in the winter. Storing a lot of heat in the summer from solar thermal collectors can provide a lot of heat in the winter, saving lots of energy and money.
As the owner of one of the relatively few ground source heat pumps in the UK I can say that air sourced heat pumps are not a good idea even in this climate. The co-efficient of performance (COP), the ratio of heat out to electrical energy in is critically dependant on keeping as low as possible the temperature differential between the hot water in the heating system and the cold water in the underground tubes or air heat exchanger.
Carnot's theorem places an upper limit on this. With a hot temperature at 45°C and a cold temperature at 0°C you could only possibly get a COP of 7 but with a cold temperature of 10°C and a hot temperature of 32°C you can theoretically get a COP of almost 14. In practice you get only a fraction of this value but the drop off in COP with increasing temperature differential is still dramatic. On my system the specification is a COP of only 2.2 for a 0°C to 45°C differential and a COP of 5.2 for a differential of 10° to 32°C. I have installed an energy meter flow meters and differential thermocouples on my system and it performs to specification.
With an air heat exchanger, because of the practical limits on size in a domestic setting, the cold water has to be several degrees below the air temperature in order to suck 10kW or more of heat out the air and without a powerful fan consuming lots of energy the air near the heat exchanger is colder than the normal air further away. The upshot is that with air at 5°C the cold end water is likely to be -1 or -2°C. This has a disastrous effect on the COP and I believe it is common for air sourced units to give up at air temperatures of a couple of degrees or so and turn themselves into resistive heaters. My ground sourced unit has never had the cold end water below 8°C even when the air was -5°C one December night.
The other end of the problem is to keep the heating water temperature down. Conventional radiators of the size common in the UK will not do the job. They are
designed to take water at 60°C or more. Fanned convectors are better but to be able to heat the room to 22°C with water at 35°C requires the sort of heated ares
a you get with underfloor heating. This is no great problem with a newly built house but retrofitting this to an old house as I have done is no small task.
You are usually advised to fit a buffer tank between the pump and the heating system to stop short cycling the pump. With the cheap offpeak electricity available in the UK (my price is 3.3p/kWh offpeak against 12p/kWh else) you can use the buffer tank to store up heat overnight. I would like to experiment by putting phase change material (fancy paraffin wax in the tank to increase the heat storage at almost contant temperature.
Amorphous PV panels are not better in cloudy weather, Monocrystalline are always more efficient. It is just that the differential between them is less in cloudy conditions and they cheaper per unit area.
The very best glazing units are better than a brick wall as they gain solar energy. Averaged over a year there can be a net energy gain.
They have been designed to give greater efficiency at low temperature than was available with earlier models, and also do a bit better with outsize radiators then the old ones, although of course not as well as they would with underground heating.
It is all a matter of trading off install costs against running costs, and having to supplement the heat on a few days a year by switching to electric is probably a better buy for many than having very high install costs.
As for the efficiency of PV panels between amorphous and monocrstalline, sure the latter is more efficient in terms of power by area, but unless you have severe space problems that is not the important metric, as panels are sold by their rated output.
And you are going to get more of that output on a cloudy day from the amorphous silicon, and they are also much better at producing good output when dirty or there are a couple of leaves on them: http://www.solarvoltaic.com/images/doc/solar%20abstract.pdf
solar%20abstract.pdf
I don't have natural gas at my home, just electricity, and one of the first things I did was put in an air-source heat pump. For various reasons, I undersized it (and knew I was under sizing it even, dammit) so although I'm unequivocally happy with the unit's performance and reliability, there are still too many days here in Northern California when it isn't up to the job. It's a Sanyo 12KHS51 mini-split model (compressor outside, air exchanger inside; quiet and unobtrusive). Combined with fiberglass frame, double-glazed, low-e, argon filled windows with a spectrally selective film from Bekeart, I figure I dropped my heating bills to half the previous owner's bill.
I'm now looking at replacing my Sanyo with the latest from Fujitsu (but the next size up), the Halcyon. The SEER is 21 (!!) compared to my SEER of just 10. I know that technology won't save us, but it sure does march on...
This conversation is especially timely for me as I will be meeting with an electrical utility to discuss various DSM initiatives now under consideration, including the retrofit of air source and geo-exchange heat pumps in electrically heated homes. As I've stated here before, I've always considered high efficiency air source heat pumps a better value overall, at least in our milder Maritime climate, but I haven't looked closely at the numbers until now.
To better prepare myself for this meeting, I've downloaded ten year's of hourly temperature data for the Halifax area and built a spreadsheet to test various scenarios (it's 673 pages long, but the first two pages are available in PDF format here: http://www.datafilehost.com/download.php?file=d4474884). According to the Nova Scotia Department of Energy, the spacing heating demands of a conventional new home based on our construction standards and local climate is approximately 50 million BTUs (older homes are rated at 80MM BTUs and an energy efficient R2000 home is pegged at 30MM BTUs). In the standard scenario, I've assumed internal heat gains from lighting, appliances, passive solar, occupants, etc. would be sufficient to maintain indoor temperatures until outside temperatures fall below 15C/59F. I've also assumed heat loss below this point averages 200-watts per degree C (I appreciate heat loss is not linear and other factors such as wind play a large role, but this level of detail goes well beyond my abilities to model here and probably wouldn't alter the final results appreciably).
I selected the Fujitu 12RLQ and 15RLQ as our air source units and estimated their installed cost at $3,500.00 and $4,000.00 respectively (an amount roughly double their wholesale cost).
The ten-year average space heating requirements of our reference home is 15,024 kWh/year. If the results are valid, the smaller of the two units can supply roughly 76 per cent of overall demand and the larger, 79% -- this assumes the heat supplied can be adequately distributed throughout the home, which is unlikely, but that's something I'll put aside for now. Backup heat, to be provided by current heating system, is estimated to be 3,602 and 3,126 kWh/year respectively.
The financials, as I expected, are strong, with annual savings in our base year of roughly $840.00 for the 12RLQ and $880.00 for the 15RLQ. This puts the simple pay back at under four years for the former and five years for the latter, assuming a modest 6% escalation in electricity costs. The internal rates of return are 26 and 23 per cent and the corresponding 10-year NPVs are $4,665.00 and $4,504.00, assuming a cash discount rate of 5%. Overall, a pretty solid investment.
Surprisingly, the numbers for the geo-exchange system were not nearly as good and I'm wondering if I've made some poor assumptions or if my calculations are flawed. I've assumed a capital cost of $18,000.00, which includes the installation of ductwork, an average COP of 4.0 and that the heat pump can supply 100 per cent of the home's space heating and domestic hot water needs. The combined annual savings in our standard scenario are $1,482.00. This provides us with a pay back of just under ten years (again, assuming a 6% escalation in utility rates), an internal rate of return of 1.4% and a ten-year NPV *loss* of just over $3,100.00. I had thought the inclusion of the DHW component would minimize the gap between these two systems but that doesn't seem to be the case. So I'll pose the same question I asked in another forum: Am I missing something obvious or are the numbers I used unrealistic? I don't want to unfairly criticize a technology if it can help customers save money and assist the utility in meeting its goals.
Bear in mind the target homes are electrically heated and would be, in most cases, reasonably energy efficient; again, the space heating requirements are likely to be in the order of 50MM BTUs/year or less. The vast majority would be heated with conventional electric baseboard units, although a smaller number could be in-floor or radiant panel, ETS, electric boilers and forced air furnaces – with the exception of the latter, there would be no existing ductwork.
Any feedback would be appreciated as residential heating systems are not my speciality and I don't wish to publically embarrass myself or my company. And if anyone wants to examine the spreadsheet internals, I'd be happy to email them a copy if they so desire.
I think that I found a flaw. Air source heat pumps output declines significantly at cooler temperatures. More electricity AND less heat as the temp drops. This adjustment is not apparent in your spreadsheet.
In New Orleans, I found that heat pumps sized for a/c cooling load could provide adequate heat down to about +3 C (with interior heat from office building). GREAT for us (rarely below 0C), minimal gas heat supplement.
On an province wide basis, this has strong implications. Minimal demand at 8C (air source works wonderfully), MUCH higher demand (and resort to resistance heat) at, say, -20 C. TOOOO much for grid :-(
If you would like to talk, send me an eMail (click my name and it is in my profile).
Check out information in this thread on the new Eco-Cute CO2 air pumps - they are not yet in the States, Japan only, but they are more efficient and good for down to -20C
Thanks for your comments and for your kind offer to assist; both are much appreciated and I might just take you up on that.
Actually, the spreadsheet makes adjustments for both output and power consumption based on outdoor ambient temperature. At 8.3C/47F, the Fujitsu 12RLQ produces 4.68 kW of heat and its power consumption is 1.25 kW (COP = 3.75). At 24C, heat output climbs to 6.18 kW, but so too its power demand -- maximum demand is said to be 2.14 kW. At -15C, we're told heat output falls to 0.9 kW; I don't honestly know the exact numbers, but I'm guessing at this point its COP runs in the range of 1.75 to 2.0 and that periodic defrosting of the outside coils kicks us closer to 1.5 or perhaps 1.8. I wish I had better numbers to work with and as soon as I find them I'll incorporate them into the model.
That said, based on published specs, we would expect heat output to rise an average of 0.094 kW per degree C and for our purposes, I rounded that down to 0.09 kW/C. Likewise, for each degree above 8C, power consumption should increase by no more than 0.059 kW and I rounded that up to 0.06 kW. On that basis, I'm reasonably confident our performance estimates are accurate for temperatures 8C and above. When temperatures fall below 8C, we assume heat output drops by 0.16 kW/C which is in line with published specs. With regards to power demand, one would expect it to fall largely in proportion to heat output, but this would be tempered by defrost demand; in our model, I assumed power demand would only fall by just 0.004 kW/C which is far more pessimistic than need be. For example, at -15C, we know heat output is 0.9 kW, but my calculations have power demand at 1.16 kW, giving us a negative COP when, in fact, we know it would be positive. I figured it would be better if I intentionally underestimated performance rather than the other way around so, if anything, the numbers should be even better than what we show here.
at -15 C... but my calculations have power demand at 1.16 kW, giving us a negative COP when, in fact, we know it would be positive.
Actually not. It is entirely possible for a heat pump to generate less heat than electrical resistance heat (COP < 1.0). Given the stress on the equipment, and defrosting, it is better to turn off the heat pump and go to resistance heat (or oil) before this happens (at COP 1.5 or so). 28 F or so depending upon the model.
It is entirely possible for a heat pump to generate less heat than electrical resistance heat (COP < 1.0).
Hi Alan,
I'd be shocked if a heat pump's COP would be allowed to fall below 1.0 within its normal operating range; presumably manufacturers would avoid this for all the obvious reasons. As mentioned, I don't have the operating specs on the Fujitsu 12RLQ (HSPF = 10.55), but I do have them for a York BHX024 which is a less efficient unit with an HSPF of 8.0. At -23C and with 21C dry bulb temperature over the evaporator coil at 800 CFM, the BHX024 produces 2.43 kW of heat and has a power draw of 1.25 kW, which includes the blower. So even at -23C, a full 8 degrees below the -15C cut-off of the Fujitsu, the COP for this particular heat pump is a still respectable 1.95. Defrosting will obviously take the final number down somewhat, but I couldn't imagine a scenario short of entombing the outdoor compressor in a thick block of ice where more energy would be expended performing this task than what would be gained through normal operation.
I tend to believe my numbers are, if anything, unfairly conservative but, again, this isn't my area of expertise, so I would encourage you and anyone else to challenge my assumptions and poke holes in my arguments.
Actually,
Air Source Heat Pumps are designed to fall below a COP of 1.0 when the outdoor temperature gets near or below freezing. What happens is the outdoor coil begins to Freeze up. Then, to combat this, by design, is the Unit switches to Air Conditioning mode to generate heat on the Outdoor coil, thereby cooling indoors. Then, since it is winter, and you want heat, the resistance coil turns on, thereby taking cooled air and reheating it, and heating it more in order to heat your home. This is painfully inefficient. And is what in fact has given the Heat Pump industry a serious black eye in the majority of North America. And sadly, Ground Source Heat Pumps have had to work hard to rid this stigma, since they are entirely different and not prone to the same problem.
Now I don't know about this fujitsu model. It must use a different refrigerant to make this possible.
Air Source Heat Pumps are designed to fall below a COP of 1.0 when the outdoor temperature gets near or below freezing
Hi Saratoga Peak,
Frankly, I don't see how this is possible and it certainly doesn't reflect my own experience. Air source heat pumps are rated by their HSPF (Heating Season Performance Factor), which is a ratio between how much heat they produce over the heating season versus the amount of energy they consume, in total; obviously, higher numbers are better. The Fujitsu 12RLQ has a HSPF of 10.55 (Zone 4). To convert this to its "seasonal COP", you divide this number by 3.4, which gives us a COP of 3.1. The York product I mentioned above has a HSPF rating of 8.0, so its seasonal COP is 2.4. Just to be clear, these numbers take into consideration the energy used to defrost the outside coils. I should also add that Halifax, N.S. is located in Zone 4 and our heating degree days number 7,800, which means our winters are as cold as those of Minneapolis, MN (not exactly tropical by any means).
Prior to installing my ductless heat pump, I used, on average, a little over 2,000 litres of heating oil a year for space heating and domestic hot water purposes. The following winter, this number dropped to 827 litres and last year it came in at 830 litres. My records show my DHW related consumption during the summer months averages 1.2 litres/day and about 1.5 litres/day during the winter months when water inlet temperatures are lower, I do more laundry (bulker and heavier clothing) and when longer (and hotter) showers are preferred. On this basis, I can reasonably assume 500 or so litres a year can be attributed to DHW needs, with the balance related to space heating. Thus, with the addition of my heat pump, my space heating consumption has fallen from about 1,500 litres/year to 330 litres, for a net savings of 1,170 litres/year. [My home, btw, is a 2,500 sq. ft., 40-year old Cape Cod that has been extensively upgraded in terms of its thermal efficiency, with a space heating demand that places it somewhere between a conventional new home and a R2000 equivalent.]
My oil-fired boiler has an AFUE of 82%, which means I net about 8.77 kWh of heat from each litre of heating oil. Multiplying 1,170 litres x 8.77 kWh/litre, tells me my heat pump is providing me with an average of 10,260 kWh of heat over the course of the heating season. My electrical consumption averages 17 kWh/day during the summer months and climbs to 40 to 43 kWh/day during the coldest winter months when the poor little guy is working flat out. Taking a look at my most recent power bill, here's how the numbers break out (total consumption / days in billing cycle / kWh/day):
For the period ending:
January 08 -- 2,540 kWh, 59 days, 43 kWh/day
November 07 -- 1,527 kWh, 62 days, 25 kWh/day
September 07 -- 1,136 kWh, 62 days, 18 kWh/day
July 07 -- 1,043 kWh, 62 days, 17 kWh/day
May 07 -- 1,848 kWh, 62 days, 30 kWh/day
March 07 -- 2,397 kWh, 58 days, 41 kWh/day
January 07 -- 2,332 kWh, 58 days, 40 kWh/day
Past Year: 10,491 kWh, 365 days, 29.7 kWh/day
Our heating season basically kicks off October 1st and eventually tapers off towards the latter part of May, so if we look at the consumption for just this period, I used a total of 7,548 kWh over the span of some 210 days, which is an average of 35.9 kWh/day. From that, I can subtract what would be used for other household needs (i.e., lighting and appliances) which, based on my summer usage, seems to be in the range of 17.5 kWh/day. If these numbers are more or less correct, my heat pump consumes a little less than 3,900 kWh/year but provides me with just over 10,000 kWh/year in heat. On this basis, my seasonal COP should be in the range of 2.5. Note too that my heat pump has a HSPF of 7.2 and the Fujitsu has a HSPF of 10.55, so the Fujitsu should be, in theory, 1.5 times more energy efficient than my own.
My apologies for the long post, but I wanted you to understand my own "real world" experience with air source heat pumps. I'd be happy to answer any questions you have and provide you with more information if it would be helpful.
Greetings; I am in Sydney, NS and was wondering if you know anyone else in halifax who is researching peak oil ?
You do not have any email contact info in your personal info section. Can you email me ?
Assuming that the 'Halifax' in your handle refers to Halifax, Nova Scotia there is actually an air-source heat pump designed specifically for the Canadian climate, although I realise of course that your climate is more maritime than many areas.
This air-source pump is OK at down to -30C.
Efficiencies should approach ground source pumps, they say.
The site also includes a cost calculator for different towns in Canada and the US, although the one for Halifax has a glich, as it is under 'Halifax Int'l Airport, which crashes the program.
Many thanks for the links. I've been following the development of this heat pump fairly closely and I think it holds tremendous promise. As you may know, some of the first generation "cold weather" heat pumps in utility field trials were plagued with quality control issues, but that's not uncommon with any new technology. I hope it will be a huge success for them.
The narrow strip of land that hugs the south-eastern portion of the province stretching from Yarmouth in the south to Halifax in the north is considerably milder than other parts of the province; we're rated as Zone 4 whereas the rest of Nova Scotia is classified as Zone 5. In fact, our temperature here at harbour side are commonly two to three degrees warmer than even the airport readings just a few km inland.
I log every single hour my heat pump operates in a spreadsheet and calculate its relative performance based on these airport readings. I estimated my seasonal COP last year at 2.48; in reality, it's higher than this due to our slightly milder micro-climate.
The nominal COP of the Fujitu 12RLQ is 3.75 (at 47F/8.3C) and based on airport data for the past ten heating seasons, I've calculated its seasonal COP to be 3.26 (and as I've stated above, I believe my estimates are decidely conservative). I suspect one reason why our performance is so good is that given our truly maritime climate, we seldom get sharply bitter cold weather, and when we do, it doesn't last very long. In addition, we have unusually long, cold spring. Whereas Toronto come May can be basking in 30+C temperatures we consider ourselves lucky if we break 15C. Looking at the rolling COP as each day passes, you can clearly see how our extended heating demand during the months of April and May move our seasonal average upward.
They are not available outside Japan yet, but if you have concerns regarding the reliability of the Canadian model you might possibly have more confidence in Japanese engineering, with the added fact that they have installed very many of their new carbon dioxide based Eco-Cute heaters for several years.
The big thing is that they have a COP of up to 4.9.
I don't know how that would fit into your schedules but it might be worth waiting, as I believe they might be available outside Japan in the next year or so.
That they are good for down to -15C can't be bad either, even if not strictly needed in Halifax.
I think they're just now hitting the European marketplace and I suspect they'll eventually make their way here, but it likely will be a few more years yet. Someone in another thread spoke of "technological hard ons" and I confess there are two things that stir deep passion; one is this: http://www.allpar.com/cars/dodge/challenger.html and the other (don't laugh) is the Eco-Cute. As someone who abhores energy waste, I'm ashamed to admit the former, but the '74 Challenger was my first set of wheels and thirty-five years later, it still holds tremendous emotional appeal... chalk it up to that left-side, right-side of the brain thingy.
In any event, I would dearly love to replace my oil-fired boiler with an Eco-Cute. I believe Sanyo recently announced an enhanced version that works efficiently at temperatures at or below -20C. Pardon my Japanese, but that really "蹴りのろば!
At this point, almost two-thirds of our fuel oil consumption is DHW related. Five hundred litres/year is a trivial amount compared to most households, but since it's the only low hanging fruit remaining, it's the logical place to target. I'm struggling with this, but I'm thinking of adding a Nyle heat pump to take on this responsibility, assuming I can somehow attach it to plumbing that connects my boiler and the SuperStor Ultra cylinder.
Right now, I can shoot down to Bangor and throw one in the back of the Chrysler for a little over $800.00 CDN. With a COP of 2.0 to 2.4, it would cut our water heating costs by more than half, plus minimize or even eliminate the need to run the dehumidifier during the summer months (after our heat pump, probably our next biggest power draw). Between May and October, our dehumidifier averages between 5 and 10 kWh/day, so the Nyle could assume full responsibility for this task and, in the process, provide us with free hot water. Even though our DHW requirements are extremely modest, once you factor in the dehumidifier savings, our simple payback is less than three years. My unnatural lust for the Eco-Cute is the only reason why I'm hesitating. ;-)
You obviously know a great deal more than I on all these subjects!
On top of that, the requirements are radically different between America and Britain - no need for de-humidification here, and not much for air-conditioning.
One thing which caught my eye though was reclamation of heat from waste water via a coil - at the cost of your bills it won't pay-back in a reasonable time though.
I had considered adding a heat recovery device to our shower drain but there's only the two of us and our low-flow shower head has an on/off control that allows us to conveniently turn off the water as we soap up, so a typical shower might consume 20 to 25 litres of hot water at most, and I suspect the actual number is closer to 15L. That's less than 1 kWh of heat demand and if a recovery device could recoop 40 per cent of that, our savings would be less than $3.00 a month; strictly on economic terms, a non-starter.
As an alternative, I heat our wash water during the summer months with a 50 metre garden hose that I roll out on the back patio. An hour exposed to direct sun can raise water temperatures by 40 or 50C. And by the time the front loader has finished its first load, the hose has come back up to temperature and is ready to do the next. By scheduling laundry on the days when the sun does shine (admittedly a daunting task given our maritime weather), I've trimmed our fuel oil consumption between May and October by an average of 6.0 litres/month, and at no cost to boot! It's enough to bring tears to any Scot's eyes. :-)
The efficiency of these devices is limited, according to thermodynamics, to the temperature differences between the house and the medium from which the heat is being extracted. Sure air pump heat pumps are as efficient as ground source heat pumps when the heat source has about the same temperature ( i.e., 50 degrees F). But as the air temperature drops, then air source heat pump efficiency and capacity drops through the floor. Employing tweaks to improve the efficiency of air source heat pumps should help ground source heat pumps as well.
I've been discussing the performance of GSHPs with a professor of architecture and engineering at the University of Waterloo. He's done extensive in-field evaluations of these products and tells me the COP numbers are often significantly lower than expected, particularly where heating and cooling demands are not well balanced (in my province, for example, our heating season spans late September/early October and runs through late May/early June and we have no cooling requirements to speak of). In addition, during the shoulder seasons, daytime air temperatures routinely exceed ground temperatures, especially late spring when ground temperatures are at their lowest due to natural thermal lag and where the earth in the immediate area of the supply lines has been further chilled by the operation of the GSHP.
Along these lines, the ten-year mean air temperature for Halifax for the months of October and November and April and May is 7.2C (as noted above, the Fujitsu 12RLQ has a COP of 3.24 at 8.3C and 7.2C is within spitting distance of that mark). The ten-year mean temperature for the full heating season which, for our purposes, I've designated as October 1st through May 31st is 2.2C. According to Natural Resources Canada, our average "deep ground temperature" is 9C and I presume this number is somewhat lower during the winter months due to normal seasonal variations and would fall further as heat is extracted over a seven or eight month period. Looking at the entire heating season, the spread between air and ground temperatures may not be as great as one might think.
In any event, if we assume a heat demand of 15,000 kWh/year, at $0.10 per kWh, a homeowner would expect to pay $1,500.00 a year to heat with electric resistance. A high efficiency air source heat pump with a HSPF of 10 would lower this cost to $500.00/year and a ground source heating system with a COP of 4.0 would get us to down to $375.00. The additional savings, in this case, are $125.00, and if we add another $250.00 for domestic hot water, our net savings are $375.00. If we double heat demand to 30,000 kWh/year and double electricity costs to $0.20 per kWh, our incremental savings reach $1,000.00/year ($500.00 for space heating and a further $500.00 for DHW production). It sounds great, but if the installation costs are $10,000.00 or more above what I would expect to pay for a conventional air source heat pump, how do I stand to benefit?
You live in a similar latitude as me as I live in Ann Arbor, Michigan. The efficiency benefit of a ground source heat pump (GSHP) over air source heat pumps (ASHP) are obvious and you seem to agree with that, although I did not verify your numbers. I will then address several points that you make.
One is that with a closed loop GSHP, the ground will tend to be cooler at the end of the winter (perhaps approaching freezing or 32F) and thus an ASHP would actaully be more efficient than the GSHP. That is potentially a true statement for the daytime but as long as the nightime temperatures are low enough, the GSHP would still be more efficient. If you are talking about when the nightime temperatures are also higher than 32 degrees even at night, the energy gain from solar heating though is likely high enough that neither system would run much at these higher temperatures (remember that insulation is sized to deal with zero F degree days), thus this warmer part of the year would have very little impact on costs. Just a sidenote, my lot is adjacent to a pond so the water table is VERY high. I doubt that the ground temperature will decrease to under 40F for my system because of the very high water content in the soil.
An important point to make is that the impact on global warming will tend to shift our climate. We will spend more of our energy on cooling going into the future compared to heaating, thus at our latitude, the heating of the ground will be more balanced with the cooling of the ground. Also, the solar affect tends to increase the cooling load for the summer months greater than what the average temperatures would suggest.
All this discussion is moot if the GSHP is an open loop system, which has improved thermal efficiency but trades off with pumping losses.
I will not agonize whether your cost numbers are right or wrong. Using them on their face value, the economics suggest that the payout for a GSHP at current energy prices over an ASHP is on the order of 30 years. This is not that much different than a GSHP over a natural gas furnace with air conditioner. It all depends on whether you want to trade higher capital costs for operating costs.
The second part of your message gets closer to the issue for me, and that with energy prices expected to increase, the payout is expected to be, using your simply adjusted cost numbers, 10 years or less. That is a much more easy step to take when installing a system cost that is expected to last over 30 years. The other part of this is that I am an environmentalist. Thus I gain a sense of satisfaction on the fact that the GSHP will reduce greenhouse gas emissions over a natural gas furnace or an ASHP. By that way, assuming coal-fired electricity generation, the ASHP will have a larger CO2 impact than both GSHP and natural gas furnace/air conditioner. Even assuming coal-fired electricity, the GSHP will have lower CO2 emissions than a natural gas furnace/air conditioner.
Thanks for your comments. As is true with most things in life, we're often forced to make trade-offs and, in this case, I'm willing to sacrifice some efficiency for lower price -- the exact numbers we could probably toss about for days. I decided my limited resources would be better spent elsewhere (i.e., improving the overall efficiency of my home's thermal envelope), but if someone is willing to spend more for a system they percieve to be better for whatever reason then, obviously, price may not be the best metric by which to judge such investments. I certainly applaud you for taking into consideration these other factors. However, as valid as these other points may be, if we are to recommend a particular technology and especially if we are to recommend it over a competing technology, we can't ignore or simply gloss-over the financials. No one has properly addressed this aspect, at least to my satisfaction, and in the absence of such, I can't in good faith recommend these systems.
BTW, just as one more random data point... earlier today I asked a contractor who installs these products in the Moncton area (in the neighbouring province of New Brunswick) how much a 3 tonne GHSP might cost. He said a typical closed loop system in the case of new construction runs in the range of $25,000.00 and an open loop version might push us closer to $30,000.00. I'm curious, do these numbers strike you as high, low or just about right?
Triple glazing, standard in Sweden, eliminates condensation problems such as you get with double glazing, as it is almost as good an insulator as the wall around it.
IIRC double glazing (not high E) is around R1.5 while triple glazing runs around R3. This is hardly 'almost' as good as a 6" wall at ~R25 - 30. Not to say of course that triple glazing is not a good idea.
"Still nowhere near as high as a decent insulated wall, though."
Because a window lets in sunlight and a wall does not, it is possible during daylight hours for a window to let have a net energy gain which a wall cannot. If the walls inside of the insulation have a high thermal mass this energy can be stored at least overnight. This is used in passive solar houses. Experiments have been done using micro-spheres of phase change material incorporated into a thick plaster coating of the wall to increase the thermal mass of interior walls as the waxy material absorbs a large amount of latent heat in warming up over a few degrees around its melting point.
The British Fenestration Rating Council has a rating system that combines the insulation value with the solar gain factor and any air leakage in opening windows. A positive rating means a net energy gain over the year and a negative value a net energy loss. With low iron content glass to maximize solar gain and soft coated low emissivity glass triple units with Xenon gas fill and the best spacers a positive rating is possible. The metric U value of such units can be as low as 0.7 W/m².K (Imperial R = 8)
> Because a window lets in sunlight and a wall does not, it is possible during daylight hours for a window to let have a net energy gain which a wall cannot.
Absolutely. Which is why I designed my house using passive solar techniques.
>With low iron content glass to maximize solar gain and soft coated low emissivity glass triple units with Xenon gas fill and the best spacers a positive rating is possible.
That depends on where the building is located (i.e., Los Angeles vs Chicago vs. Anchorage)
>The metric U value of such units can be as low as 0.7 W/m².K (Imperial R = 8)
Such windows tend to have relatively low solar heat gain coefficients (SHGC), significantly reducing the incoming solar heat. I favor dual pane (with minor low-E) with insulated window shades of one kind or another, even if it means raising them on sunny days and lowering them at sundown. My house is in a moderate temperate environment; if I were in Calgary, triple pane might make more sense, at least on the north, east, and west windows. I would still use insulating shades, but that's just me.
Be wary of argon filled windows. We just spent $7,000 for installation of 7 of the best high efficiency windows, only to find out that on average, about 5% of the argon leaks out each year. If I had the money to spend over, I think I'd get removable internal and external acrylic storm windows attached with magnetic strips that can be removed in the summer.
Ground source heat pumps are now being installed in around 97% of new builds in Sweden, I understand.
Here in the UK with a maritime climate we don't even nee to go to that much expense as we can install the far cheaper air source heat pumps as it rarely drops far below zero for long periods.
Needless to say the UK government is providing no encouragement or support, whilst in France they put in 50,000 a year.
A couple of alternative suggestions which may provide a quicker pay-back:
You can now buy heat reclamation coils for your waste from hot water.
They are a copper coil, which feeds cold water around your waste, and returns it to your tank heated.
If it is in a shower that is all you need, as the water comes in and goes out at the same time.
If it is for the washing machine or whatever you will need another tank, as the water does not flow out at the same time.
Another system which may provide better ROI is solar thermal panels.
I would suggest the vacuum evacuated tube type, and to insulate them well, as they provide more hot water on cloudy days than the alternatives.
You can buy some which are designed to be combined at a later date with PV panels- of these amorphous silicon is far better in cloudy weather.
You might also consider buying a few square feet of aerogel at $5/foot, as with it you can insulate those areas that are difficult by traditional means, such as the corners of windowframes.
Triple glazing, standard in Sweden, eliminates condensation problems such as you get with double glazing, as it is almost as good an insulator as the wall around it.
Finally, you could consider installing a greenroof, which might be economical when you need to replace your existing roof:
http://environment.newscientist.com/article/dn12710-green-roofs-could-co...
'Green roofs' could cool warming cities - earth - 28 September 2007 - New Scientist Environment
Much better insulation, and they look great too!
You may instead want to explore solar-heated borehole thermal energy storage, as it has been implemented at this subdivision near Calgary, though your system could be much smaller;
http://www.dlsc.ca/how.htm
See the video for full explanation;
http://www.dlsc.ca/DL_11_28_web.mov Quicktime
http://www.dlsc.ca/DL_web_11_23.wmv Windows Media Player
Solar energy is captured year-round by rooftop solar collectors and stored in the ground by pumping the heated fluid into borehole piping loops
Overview
This system will provide 95% of the heat for these homes near frigid Calgary. Your system would be much smaller, maybe a couple of boreholes and no tanks. Here's an photo of the actual completed community;
That is a nice project, but it requires a new development with district heating. I think that an individual home could to something similar with a ground source heat pump and solar thermal collectors.
During the summer, the hot water is circulated down into the ground heating the soil and storing the energy. During the winter months, when it is cloudy and you can not use solar thermal heating, you can draw from the heat stored in the ground to heat the home using the heat pump.
Even without solar collectors, ground-source heat pumps store and reuse energy. When cooling the house for the summer, heat is rejected to the ground. When winter comes, that heat can be extracted from the ground to heat the house. As spring approaches, the ground has been cooled after the witner and is thus is a more efficient medium for cooling the house.
Retsel
Yes, however many places in the U.S. do not require much AC in the summer but require a lot of heating in the winter. Storing a lot of heat in the summer from solar thermal collectors can provide a lot of heat in the winter, saving lots of energy and money.
As the owner of one of the relatively few ground source heat pumps in the UK I can say that air sourced heat pumps are not a good idea even in this climate. The co-efficient of performance (COP), the ratio of heat out to electrical energy in is critically dependant on keeping as low as possible the temperature differential between the hot water in the heating system and the cold water in the underground tubes or air heat exchanger.
Carnot's theorem places an upper limit on this. With a hot temperature at 45°C and a cold temperature at 0°C you could only possibly get a COP of 7 but with a cold temperature of 10°C and a hot temperature of 32°C you can theoretically get a COP of almost 14. In practice you get only a fraction of this value but the drop off in COP with increasing temperature differential is still dramatic. On my system the specification is a COP of only 2.2 for a 0°C to 45°C differential and a COP of 5.2 for a differential of 10° to 32°C. I have installed an energy meter flow meters and differential thermocouples on my system and it performs to specification.
With an air heat exchanger, because of the practical limits on size in a domestic setting, the cold water has to be several degrees below the air temperature in order to suck 10kW or more of heat out the air and without a powerful fan consuming lots of energy the air near the heat exchanger is colder than the normal air further away. The upshot is that with air at 5°C the cold end water is likely to be -1 or -2°C. This has a disastrous effect on the COP and I believe it is common for air sourced units to give up at air temperatures of a couple of degrees or so and turn themselves into resistive heaters. My ground sourced unit has never had the cold end water below 8°C even when the air was -5°C one December night.
The other end of the problem is to keep the heating water temperature down. Conventional radiators of the size common in the UK will not do the job. They are
designed to take water at 60°C or more. Fanned convectors are better but to be able to heat the room to 22°C with water at 35°C requires the sort of heated ares
a you get with underfloor heating. This is no great problem with a newly built house but retrofitting this to an old house as I have done is no small task.
You are usually advised to fit a buffer tank between the pump and the heating system to stop short cycling the pump. With the cheap offpeak electricity available in the UK (my price is 3.3p/kWh offpeak against 12p/kWh else) you can use the buffer tank to store up heat overnight. I would like to experiment by putting phase change material (fancy paraffin wax in the tank to increase the heat storage at almost contant temperature.
Amorphous PV panels are not better in cloudy weather, Monocrystalline are always more efficient. It is just that the differential between them is less in cloudy conditions and they cheaper per unit area.
The very best glazing units are better than a brick wall as they gain solar energy. Averaged over a year there can be a net energy gain.
Of course ground source heat pumps are more efficient than air-source, but they are also a lot more costly to install.
I wonder if your figures for poor performance are looking at the very latest air heat pumps like this one from Mitsubishi?
http://www.wnibonline.com/pages/PRDetail.aspx?articleId=9302
They have been designed to give greater efficiency at low temperature than was available with earlier models, and also do a bit better with outsize radiators then the old ones, although of course not as well as they would with underground heating.
It is all a matter of trading off install costs against running costs, and having to supplement the heat on a few days a year by switching to electric is probably a better buy for many than having very high install costs.
As for the efficiency of PV panels between amorphous and monocrstalline, sure the latter is more efficient in terms of power by area, but unless you have severe space problems that is not the important metric, as panels are sold by their rated output.
And you are going to get more of that output on a cloudy day from the amorphous silicon, and they are also much better at producing good output when dirty or there are a couple of leaves on them:
http://www.solarvoltaic.com/images/doc/solar%20abstract.pdf
solar%20abstract.pdf
As for the preference for vacuum evacuated tubes for solar thermal panels, here is my reference:
http://www.viridianconcepts.com/Text%20Only%20Intro%20to%20Solar%20Power...
Introduction to Solar Power
I don't have natural gas at my home, just electricity, and one of the first things I did was put in an air-source heat pump. For various reasons, I undersized it (and knew I was under sizing it even, dammit) so although I'm unequivocally happy with the unit's performance and reliability, there are still too many days here in Northern California when it isn't up to the job. It's a Sanyo 12KHS51 mini-split model (compressor outside, air exchanger inside; quiet and unobtrusive). Combined with fiberglass frame, double-glazed, low-e, argon filled windows with a spectrally selective film from Bekeart, I figure I dropped my heating bills to half the previous owner's bill.
I'm now looking at replacing my Sanyo with the latest from Fujitsu (but the next size up), the Halcyon. The SEER is 21 (!!) compared to my SEER of just 10. I know that technology won't save us, but it sure does march on...
-Andre'
This conversation is especially timely for me as I will be meeting with an electrical utility to discuss various DSM initiatives now under consideration, including the retrofit of air source and geo-exchange heat pumps in electrically heated homes. As I've stated here before, I've always considered high efficiency air source heat pumps a better value overall, at least in our milder Maritime climate, but I haven't looked closely at the numbers until now.
To better prepare myself for this meeting, I've downloaded ten year's of hourly temperature data for the Halifax area and built a spreadsheet to test various scenarios (it's 673 pages long, but the first two pages are available in PDF format here: http://www.datafilehost.com/download.php?file=d4474884). According to the Nova Scotia Department of Energy, the spacing heating demands of a conventional new home based on our construction standards and local climate is approximately 50 million BTUs (older homes are rated at 80MM BTUs and an energy efficient R2000 home is pegged at 30MM BTUs). In the standard scenario, I've assumed internal heat gains from lighting, appliances, passive solar, occupants, etc. would be sufficient to maintain indoor temperatures until outside temperatures fall below 15C/59F. I've also assumed heat loss below this point averages 200-watts per degree C (I appreciate heat loss is not linear and other factors such as wind play a large role, but this level of detail goes well beyond my abilities to model here and probably wouldn't alter the final results appreciably).
I selected the Fujitu 12RLQ and 15RLQ as our air source units and estimated their installed cost at $3,500.00 and $4,000.00 respectively (an amount roughly double their wholesale cost).
The ten-year average space heating requirements of our reference home is 15,024 kWh/year. If the results are valid, the smaller of the two units can supply roughly 76 per cent of overall demand and the larger, 79% -- this assumes the heat supplied can be adequately distributed throughout the home, which is unlikely, but that's something I'll put aside for now. Backup heat, to be provided by current heating system, is estimated to be 3,602 and 3,126 kWh/year respectively.
The financials, as I expected, are strong, with annual savings in our base year of roughly $840.00 for the 12RLQ and $880.00 for the 15RLQ. This puts the simple pay back at under four years for the former and five years for the latter, assuming a modest 6% escalation in electricity costs. The internal rates of return are 26 and 23 per cent and the corresponding 10-year NPVs are $4,665.00 and $4,504.00, assuming a cash discount rate of 5%. Overall, a pretty solid investment.
Surprisingly, the numbers for the geo-exchange system were not nearly as good and I'm wondering if I've made some poor assumptions or if my calculations are flawed. I've assumed a capital cost of $18,000.00, which includes the installation of ductwork, an average COP of 4.0 and that the heat pump can supply 100 per cent of the home's space heating and domestic hot water needs. The combined annual savings in our standard scenario are $1,482.00. This provides us with a pay back of just under ten years (again, assuming a 6% escalation in utility rates), an internal rate of return of 1.4% and a ten-year NPV *loss* of just over $3,100.00. I had thought the inclusion of the DHW component would minimize the gap between these two systems but that doesn't seem to be the case. So I'll pose the same question I asked in another forum: Am I missing something obvious or are the numbers I used unrealistic? I don't want to unfairly criticize a technology if it can help customers save money and assist the utility in meeting its goals.
Bear in mind the target homes are electrically heated and would be, in most cases, reasonably energy efficient; again, the space heating requirements are likely to be in the order of 50MM BTUs/year or less. The vast majority would be heated with conventional electric baseboard units, although a smaller number could be in-floor or radiant panel, ETS, electric boilers and forced air furnaces – with the exception of the latter, there would be no existing ductwork.
Any feedback would be appreciated as residential heating systems are not my speciality and I don't wish to publically embarrass myself or my company. And if anyone wants to examine the spreadsheet internals, I'd be happy to email them a copy if they so desire.
Cheers,
Paul
I think that I found a flaw. Air source heat pumps output declines significantly at cooler temperatures. More electricity AND less heat as the temp drops. This adjustment is not apparent in your spreadsheet.
In New Orleans, I found that heat pumps sized for a/c cooling load could provide adequate heat down to about +3 C (with interior heat from office building). GREAT for us (rarely below 0C), minimal gas heat supplement.
On an province wide basis, this has strong implications. Minimal demand at 8C (air source works wonderfully), MUCH higher demand (and resort to resistance heat) at, say, -20 C. TOOOO much for grid :-(
If you would like to talk, send me an eMail (click my name and it is in my profile).
Best Hopes,
Alan
Check out information in this thread on the new Eco-Cute CO2 air pumps - they are not yet in the States, Japan only, but they are more efficient and good for down to -20C
Hi Alan,
Thanks for your comments and for your kind offer to assist; both are much appreciated and I might just take you up on that.
Actually, the spreadsheet makes adjustments for both output and power consumption based on outdoor ambient temperature. At 8.3C/47F, the Fujitsu 12RLQ produces 4.68 kW of heat and its power consumption is 1.25 kW (COP = 3.75). At 24C, heat output climbs to 6.18 kW, but so too its power demand -- maximum demand is said to be 2.14 kW. At -15C, we're told heat output falls to 0.9 kW; I don't honestly know the exact numbers, but I'm guessing at this point its COP runs in the range of 1.75 to 2.0 and that periodic defrosting of the outside coils kicks us closer to 1.5 or perhaps 1.8. I wish I had better numbers to work with and as soon as I find them I'll incorporate them into the model.
That said, based on published specs, we would expect heat output to rise an average of 0.094 kW per degree C and for our purposes, I rounded that down to 0.09 kW/C. Likewise, for each degree above 8C, power consumption should increase by no more than 0.059 kW and I rounded that up to 0.06 kW. On that basis, I'm reasonably confident our performance estimates are accurate for temperatures 8C and above. When temperatures fall below 8C, we assume heat output drops by 0.16 kW/C which is in line with published specs. With regards to power demand, one would expect it to fall largely in proportion to heat output, but this would be tempered by defrost demand; in our model, I assumed power demand would only fall by just 0.004 kW/C which is far more pessimistic than need be. For example, at -15C, we know heat output is 0.9 kW, but my calculations have power demand at 1.16 kW, giving us a negative COP when, in fact, we know it would be positive. I figured it would be better if I intentionally underestimated performance rather than the other way around so, if anything, the numbers should be even better than what we show here.
Best regards,
Paul
at -15 C... but my calculations have power demand at 1.16 kW, giving us a negative COP when, in fact, we know it would be positive.
Actually not. It is entirely possible for a heat pump to generate less heat than electrical resistance heat (COP < 1.0). Given the stress on the equipment, and defrosting, it is better to turn off the heat pump and go to resistance heat (or oil) before this happens (at COP 1.5 or so). 28 F or so depending upon the model.
Alan
It is entirely possible for a heat pump to generate less heat than electrical resistance heat (COP < 1.0).
Hi Alan,
I'd be shocked if a heat pump's COP would be allowed to fall below 1.0 within its normal operating range; presumably manufacturers would avoid this for all the obvious reasons. As mentioned, I don't have the operating specs on the Fujitsu 12RLQ (HSPF = 10.55), but I do have them for a York BHX024 which is a less efficient unit with an HSPF of 8.0. At -23C and with 21C dry bulb temperature over the evaporator coil at 800 CFM, the BHX024 produces 2.43 kW of heat and has a power draw of 1.25 kW, which includes the blower. So even at -23C, a full 8 degrees below the -15C cut-off of the Fujitsu, the COP for this particular heat pump is a still respectable 1.95. Defrosting will obviously take the final number down somewhat, but I couldn't imagine a scenario short of entombing the outdoor compressor in a thick block of ice where more energy would be expended performing this task than what would be gained through normal operation.
I tend to believe my numbers are, if anything, unfairly conservative but, again, this isn't my area of expertise, so I would encourage you and anyone else to challenge my assumptions and poke holes in my arguments.
Cheers,
Paul
Actually,
Air Source Heat Pumps are designed to fall below a COP of 1.0 when the outdoor temperature gets near or below freezing. What happens is the outdoor coil begins to Freeze up. Then, to combat this, by design, is the Unit switches to Air Conditioning mode to generate heat on the Outdoor coil, thereby cooling indoors. Then, since it is winter, and you want heat, the resistance coil turns on, thereby taking cooled air and reheating it, and heating it more in order to heat your home. This is painfully inefficient. And is what in fact has given the Heat Pump industry a serious black eye in the majority of North America. And sadly, Ground Source Heat Pumps have had to work hard to rid this stigma, since they are entirely different and not prone to the same problem.
Now I don't know about this fujitsu model. It must use a different refrigerant to make this possible.
Air Source Heat Pumps are designed to fall below a COP of 1.0 when the outdoor temperature gets near or below freezing
Hi Saratoga Peak,
Frankly, I don't see how this is possible and it certainly doesn't reflect my own experience. Air source heat pumps are rated by their HSPF (Heating Season Performance Factor), which is a ratio between how much heat they produce over the heating season versus the amount of energy they consume, in total; obviously, higher numbers are better. The Fujitsu 12RLQ has a HSPF of 10.55 (Zone 4). To convert this to its "seasonal COP", you divide this number by 3.4, which gives us a COP of 3.1. The York product I mentioned above has a HSPF rating of 8.0, so its seasonal COP is 2.4. Just to be clear, these numbers take into consideration the energy used to defrost the outside coils. I should also add that Halifax, N.S. is located in Zone 4 and our heating degree days number 7,800, which means our winters are as cold as those of Minneapolis, MN (not exactly tropical by any means).
Prior to installing my ductless heat pump, I used, on average, a little over 2,000 litres of heating oil a year for space heating and domestic hot water purposes. The following winter, this number dropped to 827 litres and last year it came in at 830 litres. My records show my DHW related consumption during the summer months averages 1.2 litres/day and about 1.5 litres/day during the winter months when water inlet temperatures are lower, I do more laundry (bulker and heavier clothing) and when longer (and hotter) showers are preferred. On this basis, I can reasonably assume 500 or so litres a year can be attributed to DHW needs, with the balance related to space heating. Thus, with the addition of my heat pump, my space heating consumption has fallen from about 1,500 litres/year to 330 litres, for a net savings of 1,170 litres/year. [My home, btw, is a 2,500 sq. ft., 40-year old Cape Cod that has been extensively upgraded in terms of its thermal efficiency, with a space heating demand that places it somewhere between a conventional new home and a R2000 equivalent.]
My oil-fired boiler has an AFUE of 82%, which means I net about 8.77 kWh of heat from each litre of heating oil. Multiplying 1,170 litres x 8.77 kWh/litre, tells me my heat pump is providing me with an average of 10,260 kWh of heat over the course of the heating season. My electrical consumption averages 17 kWh/day during the summer months and climbs to 40 to 43 kWh/day during the coldest winter months when the poor little guy is working flat out. Taking a look at my most recent power bill, here's how the numbers break out (total consumption / days in billing cycle / kWh/day):
For the period ending:
January 08 -- 2,540 kWh, 59 days, 43 kWh/day
November 07 -- 1,527 kWh, 62 days, 25 kWh/day
September 07 -- 1,136 kWh, 62 days, 18 kWh/day
July 07 -- 1,043 kWh, 62 days, 17 kWh/day
May 07 -- 1,848 kWh, 62 days, 30 kWh/day
March 07 -- 2,397 kWh, 58 days, 41 kWh/day
January 07 -- 2,332 kWh, 58 days, 40 kWh/day
Past Year: 10,491 kWh, 365 days, 29.7 kWh/day
Our heating season basically kicks off October 1st and eventually tapers off towards the latter part of May, so if we look at the consumption for just this period, I used a total of 7,548 kWh over the span of some 210 days, which is an average of 35.9 kWh/day. From that, I can subtract what would be used for other household needs (i.e., lighting and appliances) which, based on my summer usage, seems to be in the range of 17.5 kWh/day. If these numbers are more or less correct, my heat pump consumes a little less than 3,900 kWh/year but provides me with just over 10,000 kWh/year in heat. On this basis, my seasonal COP should be in the range of 2.5. Note too that my heat pump has a HSPF of 7.2 and the Fujitsu has a HSPF of 10.55, so the Fujitsu should be, in theory, 1.5 times more energy efficient than my own.
My apologies for the long post, but I wanted you to understand my own "real world" experience with air source heat pumps. I'd be happy to answer any questions you have and provide you with more information if it would be helpful.
Cheers,
Paul
Greetings; I am in Sydney, NS and was wondering if you know anyone else in halifax who is researching peak oil ?
You do not have any email contact info in your personal info section. Can you email me ?
Hi Gilbert,
I've send an e-mail to your hot mail account.
Cheers,
Paul
Assuming that the 'Halifax' in your handle refers to Halifax, Nova Scotia there is actually an air-source heat pump designed specifically for the Canadian climate, although I realise of course that your climate is more maritime than many areas.
This air-source pump is OK at down to -30C.
Efficiencies should approach ground source pumps, they say.
Here are the details:
http://www.gotohallowell.com/technical.html
http://www.thestar.com/article/302301
http://www.thestar.com/article/302300
The site also includes a cost calculator for different towns in Canada and the US, although the one for Halifax has a glich, as it is under 'Halifax Int'l Airport, which crashes the program.
Hope this helps.
Hi Dave,
Many thanks for the links. I've been following the development of this heat pump fairly closely and I think it holds tremendous promise. As you may know, some of the first generation "cold weather" heat pumps in utility field trials were plagued with quality control issues, but that's not uncommon with any new technology. I hope it will be a huge success for them.
The narrow strip of land that hugs the south-eastern portion of the province stretching from Yarmouth in the south to Halifax in the north is considerably milder than other parts of the province; we're rated as Zone 4 whereas the rest of Nova Scotia is classified as Zone 5. In fact, our temperature here at harbour side are commonly two to three degrees warmer than even the airport readings just a few km inland.
I log every single hour my heat pump operates in a spreadsheet and calculate its relative performance based on these airport readings. I estimated my seasonal COP last year at 2.48; in reality, it's higher than this due to our slightly milder micro-climate.
The nominal COP of the Fujitu 12RLQ is 3.75 (at 47F/8.3C) and based on airport data for the past ten heating seasons, I've calculated its seasonal COP to be 3.26 (and as I've stated above, I believe my estimates are decidely conservative). I suspect one reason why our performance is so good is that given our truly maritime climate, we seldom get sharply bitter cold weather, and when we do, it doesn't last very long. In addition, we have unusually long, cold spring. Whereas Toronto come May can be basking in 30+C temperatures we consider ourselves lucky if we break 15C. Looking at the rolling COP as each day passes, you can clearly see how our extended heating demand during the months of April and May move our seasonal average upward.
Cheers,
Paul
Hi Paul.
They are not available outside Japan yet, but if you have concerns regarding the reliability of the Canadian model you might possibly have more confidence in Japanese engineering, with the added fact that they have installed very many of their new carbon dioxide based Eco-Cute heaters for several years.
The big thing is that they have a COP of up to 4.9.
Here is the data:
http://www.r744.com/knowledge/faq/files/ecocute_all.pdf
Technology and Market Development of CO Heat Pump Water Heaters ...
I don't know how that would fit into your schedules but it might be worth waiting, as I believe they might be available outside Japan in the next year or so.
That they are good for down to -15C can't be bad either, even if not strictly needed in Halifax.
Hi Dave,
I think they're just now hitting the European marketplace and I suspect they'll eventually make their way here, but it likely will be a few more years yet. Someone in another thread spoke of "technological hard ons" and I confess there are two things that stir deep passion; one is this: http://www.allpar.com/cars/dodge/challenger.html and the other (don't laugh) is the Eco-Cute. As someone who abhores energy waste, I'm ashamed to admit the former, but the '74 Challenger was my first set of wheels and thirty-five years later, it still holds tremendous emotional appeal... chalk it up to that left-side, right-side of the brain thingy.
In any event, I would dearly love to replace my oil-fired boiler with an Eco-Cute. I believe Sanyo recently announced an enhanced version that works efficiently at temperatures at or below -20C. Pardon my Japanese, but that really "蹴りのろば!
At this point, almost two-thirds of our fuel oil consumption is DHW related. Five hundred litres/year is a trivial amount compared to most households, but since it's the only low hanging fruit remaining, it's the logical place to target. I'm struggling with this, but I'm thinking of adding a Nyle heat pump to take on this responsibility, assuming I can somehow attach it to plumbing that connects my boiler and the SuperStor Ultra cylinder.
For information on the Nyle heat pump, see: http://www.nyletherm.com/waterheating.htm
Right now, I can shoot down to Bangor and throw one in the back of the Chrysler for a little over $800.00 CDN. With a COP of 2.0 to 2.4, it would cut our water heating costs by more than half, plus minimize or even eliminate the need to run the dehumidifier during the summer months (after our heat pump, probably our next biggest power draw). Between May and October, our dehumidifier averages between 5 and 10 kWh/day, so the Nyle could assume full responsibility for this task and, in the process, provide us with free hot water. Even though our DHW requirements are extremely modest, once you factor in the dehumidifier savings, our simple payback is less than three years. My unnatural lust for the Eco-Cute is the only reason why I'm hesitating. ;-)
Cheers,
Paul
You obviously know a great deal more than I on all these subjects!
On top of that, the requirements are radically different between America and Britain - no need for de-humidification here, and not much for air-conditioning.
One thing which caught my eye though was reclamation of heat from waste water via a coil - at the cost of your bills it won't pay-back in a reasonable time though.
Hi Dave,
I had considered adding a heat recovery device to our shower drain but there's only the two of us and our low-flow shower head has an on/off control that allows us to conveniently turn off the water as we soap up, so a typical shower might consume 20 to 25 litres of hot water at most, and I suspect the actual number is closer to 15L. That's less than 1 kWh of heat demand and if a recovery device could recoop 40 per cent of that, our savings would be less than $3.00 a month; strictly on economic terms, a non-starter.
As an alternative, I heat our wash water during the summer months with a 50 metre garden hose that I roll out on the back patio. An hour exposed to direct sun can raise water temperatures by 40 or 50C. And by the time the front loader has finished its first load, the hose has come back up to temperature and is ready to do the next. By scheduling laundry on the days when the sun does shine (admittedly a daunting task given our maritime weather), I've trimmed our fuel oil consumption between May and October by an average of 6.0 litres/month, and at no cost to boot! It's enough to bring tears to any Scot's eyes. :-)
Cheers,
Paul
The efficiency of these devices is limited, according to thermodynamics, to the temperature differences between the house and the medium from which the heat is being extracted. Sure air pump heat pumps are as efficient as ground source heat pumps when the heat source has about the same temperature ( i.e., 50 degrees F). But as the air temperature drops, then air source heat pump efficiency and capacity drops through the floor. Employing tweaks to improve the efficiency of air source heat pumps should help ground source heat pumps as well.
Retsel
Hi Retsel,
I've been discussing the performance of GSHPs with a professor of architecture and engineering at the University of Waterloo. He's done extensive in-field evaluations of these products and tells me the COP numbers are often significantly lower than expected, particularly where heating and cooling demands are not well balanced (in my province, for example, our heating season spans late September/early October and runs through late May/early June and we have no cooling requirements to speak of). In addition, during the shoulder seasons, daytime air temperatures routinely exceed ground temperatures, especially late spring when ground temperatures are at their lowest due to natural thermal lag and where the earth in the immediate area of the supply lines has been further chilled by the operation of the GSHP.
Along these lines, the ten-year mean air temperature for Halifax for the months of October and November and April and May is 7.2C (as noted above, the Fujitsu 12RLQ has a COP of 3.24 at 8.3C and 7.2C is within spitting distance of that mark). The ten-year mean temperature for the full heating season which, for our purposes, I've designated as October 1st through May 31st is 2.2C. According to Natural Resources Canada, our average "deep ground temperature" is 9C and I presume this number is somewhat lower during the winter months due to normal seasonal variations and would fall further as heat is extracted over a seven or eight month period. Looking at the entire heating season, the spread between air and ground temperatures may not be as great as one might think.
In any event, if we assume a heat demand of 15,000 kWh/year, at $0.10 per kWh, a homeowner would expect to pay $1,500.00 a year to heat with electric resistance. A high efficiency air source heat pump with a HSPF of 10 would lower this cost to $500.00/year and a ground source heating system with a COP of 4.0 would get us to down to $375.00. The additional savings, in this case, are $125.00, and if we add another $250.00 for domestic hot water, our net savings are $375.00. If we double heat demand to 30,000 kWh/year and double electricity costs to $0.20 per kWh, our incremental savings reach $1,000.00/year ($500.00 for space heating and a further $500.00 for DHW production). It sounds great, but if the installation costs are $10,000.00 or more above what I would expect to pay for a conventional air source heat pump, how do I stand to benefit?
Cheers,
Paul
You live in a similar latitude as me as I live in Ann Arbor, Michigan. The efficiency benefit of a ground source heat pump (GSHP) over air source heat pumps (ASHP) are obvious and you seem to agree with that, although I did not verify your numbers. I will then address several points that you make.
One is that with a closed loop GSHP, the ground will tend to be cooler at the end of the winter (perhaps approaching freezing or 32F) and thus an ASHP would actaully be more efficient than the GSHP. That is potentially a true statement for the daytime but as long as the nightime temperatures are low enough, the GSHP would still be more efficient. If you are talking about when the nightime temperatures are also higher than 32 degrees even at night, the energy gain from solar heating though is likely high enough that neither system would run much at these higher temperatures (remember that insulation is sized to deal with zero F degree days), thus this warmer part of the year would have very little impact on costs. Just a sidenote, my lot is adjacent to a pond so the water table is VERY high. I doubt that the ground temperature will decrease to under 40F for my system because of the very high water content in the soil.
An important point to make is that the impact on global warming will tend to shift our climate. We will spend more of our energy on cooling going into the future compared to heaating, thus at our latitude, the heating of the ground will be more balanced with the cooling of the ground. Also, the solar affect tends to increase the cooling load for the summer months greater than what the average temperatures would suggest.
All this discussion is moot if the GSHP is an open loop system, which has improved thermal efficiency but trades off with pumping losses.
I will not agonize whether your cost numbers are right or wrong. Using them on their face value, the economics suggest that the payout for a GSHP at current energy prices over an ASHP is on the order of 30 years. This is not that much different than a GSHP over a natural gas furnace with air conditioner. It all depends on whether you want to trade higher capital costs for operating costs.
The second part of your message gets closer to the issue for me, and that with energy prices expected to increase, the payout is expected to be, using your simply adjusted cost numbers, 10 years or less. That is a much more easy step to take when installing a system cost that is expected to last over 30 years. The other part of this is that I am an environmentalist. Thus I gain a sense of satisfaction on the fact that the GSHP will reduce greenhouse gas emissions over a natural gas furnace or an ASHP. By that way, assuming coal-fired electricity generation, the ASHP will have a larger CO2 impact than both GSHP and natural gas furnace/air conditioner. Even assuming coal-fired electricity, the GSHP will have lower CO2 emissions than a natural gas furnace/air conditioner.
Retsel
Hi Retsel,
Thanks for your comments. As is true with most things in life, we're often forced to make trade-offs and, in this case, I'm willing to sacrifice some efficiency for lower price -- the exact numbers we could probably toss about for days. I decided my limited resources would be better spent elsewhere (i.e., improving the overall efficiency of my home's thermal envelope), but if someone is willing to spend more for a system they percieve to be better for whatever reason then, obviously, price may not be the best metric by which to judge such investments. I certainly applaud you for taking into consideration these other factors. However, as valid as these other points may be, if we are to recommend a particular technology and especially if we are to recommend it over a competing technology, we can't ignore or simply gloss-over the financials. No one has properly addressed this aspect, at least to my satisfaction, and in the absence of such, I can't in good faith recommend these systems.
BTW, just as one more random data point... earlier today I asked a contractor who installs these products in the Moncton area (in the neighbouring province of New Brunswick) how much a 3 tonne GHSP might cost. He said a typical closed loop system in the case of new construction runs in the range of $25,000.00 and an open loop version might push us closer to $30,000.00. I'm curious, do these numbers strike you as high, low or just about right?
Cheers,
Paul
IIRC double glazing (not high E) is around R1.5 while triple glazing runs around R3. This is hardly 'almost' as good as a 6" wall at ~R25 - 30. Not to say of course that triple glazing is not a good idea.
With krypton gas fill and the right low-E, a triple-pane can reach R-7.85 (and I've seen higher);
http://precisionbuild.com/winspecs.html
Still nowhere near as high as a decent insulated wall, though.
"Still nowhere near as high as a decent insulated wall, though."
Because a window lets in sunlight and a wall does not, it is possible during daylight hours for a window to let have a net energy gain which a wall cannot. If the walls inside of the insulation have a high thermal mass this energy can be stored at least overnight. This is used in passive solar houses. Experiments have been done using micro-spheres of phase change material incorporated into a thick plaster coating of the wall to increase the thermal mass of interior walls as the waxy material absorbs a large amount of latent heat in warming up over a few degrees around its melting point.
The British Fenestration Rating Council has a rating system that combines the insulation value with the solar gain factor and any air leakage in opening windows. A positive rating means a net energy gain over the year and a negative value a net energy loss. With low iron content glass to maximize solar gain and soft coated low emissivity glass triple units with Xenon gas fill and the best spacers a positive rating is possible. The metric U value of such units can be as low as 0.7 W/m².K (Imperial R = 8)
> Because a window lets in sunlight and a wall does not, it is possible during daylight hours for a window to let have a net energy gain which a wall cannot.
Absolutely. Which is why I designed my house using passive solar techniques.
>With low iron content glass to maximize solar gain and soft coated low emissivity glass triple units with Xenon gas fill and the best spacers a positive rating is possible.
That depends on where the building is located (i.e., Los Angeles vs Chicago vs. Anchorage)
>The metric U value of such units can be as low as 0.7 W/m².K (Imperial R = 8)
Such windows tend to have relatively low solar heat gain coefficients (SHGC), significantly reducing the incoming solar heat. I favor dual pane (with minor low-E) with insulated window shades of one kind or another, even if it means raising them on sunny days and lowering them at sundown. My house is in a moderate temperate environment; if I were in Calgary, triple pane might make more sense, at least on the north, east, and west windows. I would still use insulating shades, but that's just me.
Be wary of argon filled windows. We just spent $7,000 for installation of 7 of the best high efficiency windows, only to find out that on average, about 5% of the argon leaks out each year. If I had the money to spend over, I think I'd get removable internal and external acrylic storm windows attached with magnetic strips that can be removed in the summer.