Why dig??

[Xringer]

Originally Posted by AC_Hacker

Xringer,

I have seen a few papers on this by some Turkish scientists. The term is, "Solar Assisted Heat Pump".

Xringer, you've had solar HW panel experience, and you own all the tools to required to make a heat pump.

(we're waiting..........)

-AC_Hacker

Hahaha! My idea of a "Solar Assisted Heat Pump", is to use PV to supplement the grid power..


I've been thinking it would be very easy to wire up my AC current sensor
to turn on an AC SSR which would connect a GTI to the AC line..
So, when the Sanyo was using over 400w, a GTI connected to my 400w PV array,
would come on and keep the grid draw to a minimum..
(I'm just joking!)

[pick1e]

Originally Posted by Xringer

One other consideration is the land. Do you own a good sized piece of land?
Is the thin layer soil, sitting on top of a giant rock pile of granite boulders?

Or if you don't own land you can dig up- say a condo or rental like my folks. Plus with this guy if you have to move just take the unit with you and put the old furnace back in.

Two complaints about the unit you've mentioned though:

1) If they don't list a MSRP, I can't afford it.

2) Why do they list F before C in the specifications? Is our backwardness leaking across the border?

Lastly to answer the thread title- because it's fun and a good workout!

[pick1e]

Originally Posted by Ryland

I'd like to see someone combine a heat pump with solar hot water panels instead of a ground loop

I intend to eventually have a hybrid system by augmenting my ground loop with solar water heaters. This would allow me to reduce the size of my ground loop because I'd use it less often, so less long-term cooling of the ground. Also if there is a surplus from the water heaters during daytime it could be cycled through the ground to store energy for better efficiency of the ground loop during the night.

Hopefully I'll have those endeavors on my thread this summer

[RobertSmalls]

Assuming these ratings are at the maximum power draw of 2.5kW, this is a table of CoP. 2.5kW = 8500BTU/hr of electricity input, and the table shows you the output. CoP = output over input.

So at -15°C, you have a CoP of 2. At 0°C, the CoP reaches 3 (and my furnace is barely required), and with a ground loop at 7°C, the CoP would be around 3.5 for the entire heating season. The ground loop will also double your heating capacity on the coldest days of the year in Buffalo.

A CoP of 3 is roughly equivalent to the performance of a good natural gas furnace, in terms of cost or CO2.

[Xringer]

I never see 2.5kW during normal operations.
The spec says "290w to 2490w" & "4,400 to 29,000 BTU".

Of course, it's warmer here..

On Average:
* Woburn, MA is warmer than Buffalo, NY by 1°F.
* Woburn, MA is wetter than Buffalo, NY by 7.8 in.

Records:
* Woburn, MA recorded the highest temperature of 105°F in 1975.
* Woburn, MA recorded the lowest temperature of -21°F in 1961.

Due to all the heavy snow this winter, (like right now) we have not been able to use the Sanyo exclusively.
Last night, It shut off at 1AM (timer) because of the snow forecast.
(I'm trying to avoid doing a lot of defrost cycles).

But before these last few weeks, we've used very little oil.

Here's some approximate monthly power use.

kWh / Date
164 1-11
284 12-10
226 11-10
94 10-10
25 9-10
61 8-10
116 7-10
60 6-10
64 5-10
110 4-10

1204 kWh ($253)

~300 days is about 7,200 hours. On average, less than 170w per hour.

$25.30 a month for heating and cooling isn't too bad.

And, since we aren't using other (old tech) heating and cooling equipment
as much (no old window ACs at all), our monthly electrical use is actually
a bit lower than before the Sanyo.

[AC_Hacker]

Originally Posted by RobertSmalls

A CoP of 3 is roughly equivalent to the performance of a good natural gas furnace, in terms of cost or CO2.

Curious where you get this number?

There is an energy comparison tool over at Build It Solar that does the number crunching for you.

To really compare for your area, you'd need to plug in your own energy costs. But just as a test, I used the default values, which are pretty close for where I live and here are the results I found...

I get a minimum COP of 2.0 to break even in cost compared to low-efficiency Natural Gas (85%).

I get a minimum COP of 2.9 to break even in Carbon Dioxide emissions compared to low-efficiency Natural Gas (85%).

I get a minimum COP of 2.2 to break even in cost compared to high-efficiency Natural Gas (93%).

I get a minimum COP of 3.18 to break even in Carbon Dioxide emissions compared to high-efficiency Natural Gas (93%).

The Fujitsu Halcyon 9RLS (9,000 BTU/hr) and the 12RLS (12,000BTU/hr) have a HSPF = 12. If you divide the HSPF by 3.412, you get COP = 3.52.

Pretty impressive, especially considering that with a COP of 3.42, they could beat a Natural Gas furnace running at 100% efficiency (none do).

I do believe that the Carbon Dioxide numbers in the BIS calculator even include electrical power transmission losses.

So, this all generally agrees with a Swedish study done not so long ago, that concluded that Ground Source Heat Pumps were the best source of heating that used manufactured energy. I believe that their study cited a COP of 3.5 as the efficiency level for GSHO in their area.

Those little mini-splits are pretty amazing.

But some GSHPs have hit a COP of 4.5 to 5.

Regards,

-AC_Hacker

P.S.: A house built to Passive House standards is so well insulated, and efficient, that a "heating system" as we know it is not required. In fact since the cost of the heating system can be eliminated, the cost of both types of construction is roughly equal.

* * *

[RobertSmalls]

I'm paying $1.06/CCF, which is roughly $1.04/therm. I was also comparing a high-efficiency natural gas furnace that I do not own, against heat pumps which I do not own. I find the break-even CoP to be around 3.3.

Make sure you're using marginal cost, i.e. the cost for one more therm. A large slice of my bill is monthly hookup fees, and if I (incorrectly) took them into account, I'd find a price per therm of $1.74.

And yes, if I do build a Passivhaus, or a low-budget approximation thereof, I'll be looking a heating system with a low up-front cost. Efficiency isn't so important when you hardly ever turn it on.

[strider3700]

Originally Posted by RobertSmalls

Make sure you're using marginal cost, i.e. the cost for one more therm. A large slice of my bill is monthly hookup fees, and if I (incorrectly) took them into account, I'd find a price per therm of $1.74.

Why would it be incorrect to take them into account? I always include taxes and fees in my $ calculations. Those taxes and fees are rapidly moving towards 30% of the cost for each KWH on my electric bills. It makes a big difference when working out payback periods via savings.

[RobertSmalls]

Marginal cost - Wikipedia, the free encyclopedia

Unless you're contemplating getting rid of the gas dryer, stove, and hot water heater, the hookup fee is a sunk cost. You pay $149/yr for gas hookup, regardless of whether you install a furnace or a heat pump. Your first therm of the year costs $150, and each subsequent therm costs $1.

I accounted for taxes and fees that rise with my usage, and I excluded taxes and fees that don't.

[strider3700]

I hate when they do that and it's a major reason why I don't have gas at my house even though it is on the street. $150 in an upfront fee would be my summers usage of electricity.

I have to say since this thread is comparing electric heat pumps to natural gas though that fee should be included. If everyone is just ignoring big upfront costs on either service you aren't getting the full picture of what that energy source is really costing you.