Geothermal Heatpumps: An Introduction

[que3jxp]

I was asked to start a thread on GHPs and their associated costs and benefits so here we go...

For those that are unaware GHPs are basically giant air conditioners. Air conditioners are nothing more than a heat pump that is typically asked to do the impossible by way of pushing hot air into hot air.

Thanks to several laws of thermodynamics and the physics of heat transfer, if you use a heatpump with greater temperature extremes on either side of the process, the effectiveness/efficiency of the process goes up very quickly.

In a nutshell, heat energy seeks to be in a state of equilibrum (Entropy) and if there is a greater temperature variance between to areas, the rate of exchange between these areas is greatly increased.

So now that we know this, how does it benefit us?

Most people are very familiar with air conditioners and to a lesser degree, air to air heatpumps. We are all also very familiar with the fact that in the wicked heat of the summer, the A/C in the car seems to barely get the job done and that the A/C in our house seems to make the 'ole electricity meter spin like a frisbee on a caffeine rush. What has happened here is that in laymens terms, there is little or no more "space" for the heat to go and the compressor system struggles to accomplish anything at all.

How do we fix this?

Stop using the air as our heatsink/heatsource.

The ground below us at a depth below 4 feet runs an average of 40 to 60 degrees F all the time. Some areas are closer to 40 and some are even above 60. Regardless, the temperature is signifigantly lower than the ambient air temperature in the summer and is signifigantly higher than the ambient air temperature in the winter.

And this means what to me?

What it means is that heating or cooling your house or structure is FAR easier when the ground is where you get your heat from or where you move your heat to.

Even the oldest of the modern GHPs are easily capable of 250% efficiency (2.5 COP in the HVAC business). These older systems are based on having two open ended water wells that draw ground water up into a compressor system that either extracts heat or dumps it back to the ground water. The best news is that the majority of modern GHPs are typically rated no less than a COP of 3, so 300% efficient. Some are even as high as 3.6 - 3.8 COP.

So how does all of this COP and percentage business help me?

Lets look at it in the most understandable way possible....

All hydrocarbon and wood based heating systems will NEVER reach 100% efficiency. If they did or could, they would never need a chimney/exhaust pipe. Electricity, as the direct source of heat, can never exceed 100% efficiency.

Now, rather than MAKING heat, heatpumps seek to MOVE the heat around to where we actually want it. Because of this, much less effort is involved if we are dealing with reasonably large temperature differences. So for heating purposes (Cooling is a slight bit more "mathy"), if you have a COP of 3.5, for every Dollar of electricity you use, you get 3.5 Dollars of heat.

Well, that is all fine and dandy, tell me how it really helped someone...

I chose to build my house in 2000 with a "Direct Expansion" (DX) GHP. A DX-GHP is a unit that eliminates having water wells or a closed loop of ethelyne glycol that then passes to a compressor stage. The "Direct" in DX is in reference to the compressor stage being in direct contact with the ground. Physically, it is a series of vertical loops of copper pipe that contain R22 (Or the current choice in its place) vaporous coolant and pass the heat directly to/from the ground to the compressor. It is generally the least troublesome to install as it is not dependant on having ground water available (For open loop systems) and it does not risk groundwater pollution if it ruptures.

The costs involved have changed but at the time of construction, the total HVAC installation cost in my house was $11,500. This covered 3 vertical "wells", the heatpump, a backup electric element, an HRV and all of the associated ductwork. Because the system does not draw a lot of electricity, there is also no need for anything larger than a 200 amp entrance and there is a HUGE amount of wiring and baseboard installation that does not need to be done.

I did not to direct comparative pricing at the time, but due to the code requirements on HRVs and their associated ductwork, I figured that the cost difference could not have been more than $8000. At that amount, it only took me 3 years to get my "Return on Investment".

How do you know that this was the case?

Well, I was lucky enough to have my parents in the same subdivision and in a house that was built to similar construction requierments. The extra nice benefit (In this case) was that being in the same subdivision means that the temperatures are the same.

Their house is electric BB only and was built in 1993. The basement is totally finished and they make it a habbit of turning the temperatures back in unused rooms in the winter. They have also changed 70-80% of their lights to CFL. The house is a 44 x 28 Bungalow.

My house is an L shaped "raised ranch" (Stupid bedrock) that has an outer dimension of 53 x 36 and an actual square footage on the main floor of 1,648 sq/ft. At the time of the power consumption, the basement was not finished, but the 2 x 6 walls that are above the concrete were insulated and vapor barriered. I have about the same % of CFL bulbs and where the whole house is on one system, all rooms are heated the same.

The final numbers rolled out such that the KWh per sq/ft for my house was less than 50% that of my parents house. Another way to look at it is via our equalized power bills. At the time of comparison, mine was $175 per month and my parents was $249. To the sq/ft, that is $0.106 per month for me and $0.202 for my parents. If I applied their costs to my house, the bill would have been $333. So in one year, the savings would roughly be $1900.

Because this comparison was back in 2001, there is an ever increasing amount of savings due to the annual 3% increase courtesy of NB Power. With all of the increases since, the current savings is more on the order of $2500 annually.

Now for the bad news...

• The costs have gone up for installation, of course.
  
• Some municipalities do not allow even DX-GHPs to be installed. (Fredericton is one)
  
• They have a more lengthy ROI when put in after constrution.

On the upside...

• They have a VERY long life expectancy (100 years on the "wells" and 20 years on the compressor)
  
• They are a great alternative if you already have forced air.
  
• They suplement over 60% of your hot water.
  
• They are the single largest thing you can do to reduce your energy "footprint" and not go bankrupt.

For maintenance, I have had to do no more than replace a fan belt in all of the 6.5 years in the house so so far, awesome!!!

[que3jxp]

Somethings that I forgot to mention before the post on noise pollution from "HE' houses...

GHPs require space to install

There are two ways to install the coolant loops. Vertically or horizontally.

Vertical installations require the least amount of space but still take a good little bit of room. My DX installation required no less than 20 feet from each of the three loops that I needed. And each loop needs to be at least 20 feet from any large objects like your house foundation or your neighbours foundation. That means for myself, I have a 20 foot x 3equalateral triangle of NOTHING can be built here or you have to be able to move the "thing" if necessary. Fortunately, most houses only need three vertical loops.

Horizontal installations are so large that they basically are only an option for rural installations or urban installations where you own a LOT of property.

Operating noise

When in operation, there is VERY little noise. When the system has to start, you can usually hear the compressor spool up but that is about it. Only in the dead of night will you conciously hear the system and even then, it is not loud or obnoxious.

Settings and temperatures

GHPs will not set any closer than 2 degrees F for their upper and lower threshold. Our house runs at no colder than 68 F and no hotter than 70 F. If the temperature of the house is higher or lower than the two settings, it will heat or cool the house to the target temperature.

Two years ago, I decided to get a highly programmable Honeywell control panel so as to have up to 4 different time of day settings. What I learned the expensive way was that when the literature says that you should just leave a GHP be at one setting all the time, do it. The most you should do or plan on doing is to have a daytime and a nighttime setting.

There are two issues at play that cause the efficiency to plummet. The first is the fact that GHPs operate more on a "Slow and steady" principle so it is far easier if they are just set to the same temperature for as long as possible. The other issue is that if you are using the hot water heating capability of your GHP and your system is not running, then your hot water tank is now having to heat itself.

The impact of the hot water functionality

On the note of the hot water factor, two summers ago, there was a 5 day stint here in Fredericton where it was "perfect" weather. We decided to totally turn off the GHP and open the windows.

Oops....

A few weeks later the power bill comes. The billing period in question saw the power consumption jump 263 KHw higher than the AVERAGE for the whole 6.5 years that we have been here. It was some 680 KHw higher than the lowest ever in the house.

Radiant Floor heating

There are GHPs that are actually built to do nothing but heat water for in floor radiant heating. Given the benefits of radiant floor heating, one of these units with a DX forced air GHP and you would have the most efficient and comfortable house on the planet from an HVAC perspective.

A couple of arbitrary KWh numbers

• Lowest month ever Aug/Sep 2001: 1051 KWh
• Average Aug/Sep: 1419 KWh (This is also the lowest average month of the year)
  
• Highest month ever Jan/Feb 2005: 3416 KWh
• Average Jan/Feb: 2874 KWh
  
• Average overall per month over 6.5 years: 1969 KWh

[e268]

Great write up. I investigated backed in 1976 about installing heat pump for my new house in Scarborough. I was discouraged at the time because of low payback, and also supposedly high maintanence for the heat pump. But those were just the plain air type of heat pumps, and would not work once temp is below zero, but required auxiliary heating, hence poor payback. At that time, there were systems like the one you have, but I did not pursued it since I had to carry a mortgage.

I wonder if it would help improve the environment. It certainly cuts down the use of fossil fuel (gas or oil), but it consumes electricity which comes from coal or oil fire generators.

[petedran]

We built a house and got geothermal heating and moved in Oct 06. Only got 1 electrical bill so far and it was through the roof. Double anything I've experienced before. Needless to say I'm doubting weather the extra cost of geothermal was worth it. Hard to judge after only a couple of months though.

[applecran]

So if you have an existing mid efficiency natural gas furnace and an on demand hot water heater is this something that is worthwhile?

Does it work in the house in tandem with both those units, or is it a replacement for?

How exactly does it "hook in" to your forced air?

We are in BC so it never gets to hot or to cold for long, but still does sometimes and it is always nice to lower the bills.

[que3jxp]

Great write up.

Thanks!

I wonder if it would help improve the environment. It certainly cuts down the use of fossil fuel (gas or oil), but it consumes electricity which comes from coal or oil fire generators.

When you consider that my house has an energy footprint that is 50% (Or better) smaller than the average house at the sq/ft level, that means that it is a simple math formula to see that if every house that was ever built or retrofited had a GHP, then the energy footprint of that given ficticious world would be 50% smaller. For Canadians, that means that Hydro and Nuclear would be the only power sources we would have or would currently need and that we would still have power to sell to the USA.

Only got 1 electrical bill so far and it was through the roof. Double anything I've experienced before.

That is VERY bizzare. I can say that in the first few month here, that the power bills were a bit high, but that comes with any new house as you are drying it out for the first 6 to 9 months.

Can you post or PM what the model and installation type your GHP is?

You should also make sure that they are not just "guessing" you consumption. NB Power did that to me in the first three months and I had to call them to task on it. They have read the meter every time since.

So if you have an existing mid efficiency natural gas furnace and an on demand hot water heater is this something that is worthwhile?

That depends a lot on what your cost per KWh is and what your fuel costs are. Generally, electricity has a stabler price than gas or oil so that is always an attractive plus.

In the end, you will have to decide how much importance you put the long term (10+ years) value of your finances and the environment. I don't particularly subscribe to the "Al Gore" camp but I sure wanted to make sure I was not part of the problem. It is saving me boat loads of money AND I get to feel all pious about it.

Does it work in the house in tandem with both those units, or is it a replacement for?

It can go either way. If you are prone to having power outtages, and you have the $$$, then I would consider having a natural gas system as a backup.

How exactly does it "hook in" to your forced air?

The unit that is in your house looks suspiciously like an electric forced air furnace so in short, it is just like any old forced air furnace except that it is the most efficient system you can EVER own.

We are in BC so it never gets to hot or to cold for long, but still does sometimes and it is always nice to lower the bills.

Unfortunately, this is where the ROI can end up getting drug out much longer. There is, fortunately, an alternative for people in your situation. There is a company in Maine that produces an air-to-air unit called a cold climate 2 stage heatpump.

Now it is air to air so it will never be as efficient as a GHP but it makes the traditional air to air units look like junk. My uncle-in-law had no choice but to use one of them in the new house that he built in West Hills (A supposedly "Energy Smart" subdivision ) in Fredericton. This was due to the fact that the city will not allow GHPs no matter what. He has monitored it VERY closely and it does an excellent job and in the first year that he was in the house, it did not have to use the backup element.

[que3jxp]

I am going to take a bunch of pics of my system and post them later today for everyone to see what a DX-GHP installation looks like from in the house...

[Dog Byte]

Interesting. It's hard to get meaningful numbers about ROI. The issue for me is the lack of electricity. My gas boiler runs at 110 watts so hooking up a generator when the power goes out is easy. What's the actual power consumption of the heat pump?

[petedran]

Heres a link for a company that does installs and their cost savings. So far for me those "cost savings" have not materialized

http://www.geotility.ca/cost_saving.html

[que3jxp]

Here is the manufacturer of my system and one of the bigger ones on the global market. http://www.nordicghp.com/mg/ You can find my system (DX-45) in there and pull all of the electrical information you may need.

As for ROI, you need the following information in a new construction:

• Installation cost difference vs. alternatives
  
• Energy costs per unit of heat "generated"
  
• Cost of heating water separately

If you are putting a GHP into a preexisting structure that does not have duct work already in place or radiant floor piping already in place, you are going to have a MUCH slower ROI.

For new or easy retrofit, it is from 3 to 7 years.

For difficult retrofit, it is 10 to 15 years.

The above averages change dramatically if fuel/energy costs balloon.

In perspective, in 6.5 years, my equalized monthly bill has gone from $175 to $226 and my parents in their much smaller house have gone from $249 to very close to $300 the last I checked.

Take note... I am STILL paying less than what my parents were on a SMALLER house and 6.5 years ago. I have cooling in the summer and they do not!!!

[GQUEUE]

Just my 2 cents here (and up front, I will tell you I don't know very much about GHPs though I find the concept intriguing):

A close friend of mine worked as a design engineer for a company that did Geothermal systems for commercial installations (office buildings, factories, etc...). He told me that the ROI studies that his company published were largely fraudulent because they did not account for the electricity costs for fans to circulate the air throughout the facility. Because of this, none of their installations ever had operating costs consistent with the predicted expectations.

Keep in mind, that this is for commercial buildings (which are much larger and would require more air movement than a house). I have no idea whether the same applies to home installations. I understand that GW Bush has a GHP installation in his ranch for heating/cooling.

[que3jxp]

Originally Posted by GQUEUE

Keep in mind, that this is for commercial buildings (which are much larger and would require more air movement than a house). I have no idea whether the same applies to home installations.

It is not the same for normal sized houses. The internal fan is more than powerful enough.

Also, Air flow rates are still necessary to be maintained regardless of the underlying heat/cool source so your friend is incorrect in his statement. Those booster fans would be needed in any large installation.

[Monobloc]

Interesting thread. I did some research into geothermal heat pumps some time ago. The DX systems are definitely the best way to go. I'd love to go heat pump, but being a two story house with no ductwork makes it a daunting task.

The Geo aspect means no defrost cycle like on a conventional air source heat pump. Also the reason why air conditioning is so cheap in the south. BC probably has the best climate for traditional heat pumps as a large portion of the winter is spent in primary heating, with little defrost needed.

Having said that, the cost of heating in NB is quite high. $175/month for 1600-1700 sq feet. Ouch. I heat 2460 sq ft for $125/month. That's electric baseboards and electric 40 gal hot water tank. That's also with an uninsulated crawlspace ceiling, but insulated crawlspace walls. Dirt floor in there. When I used to heat the garage during the winter months (1100 sq ft, elec baseboards, thermostats set at 10C) I paid closer to $150. In an effort to save money, I turned the garage thermostats down as low as they'd go (7C) and eventually just turned off the breaker switch for them as the temperature never actually goes below freezing in there.

I wonder if insulating recommendations are different in BC vs NB? The general rule of thumb is R20 walls and R40 ceilings.

I'd probably save more money by using a clothes line. That's 5500 watts of dryer consumption per hour that I'd save.

[Jake]

Que, I am curious as to why F'ton does not allow GHPs.

[que3jxp]

The excuse (Because that is what it is) is that it can harm the water table.

See Fredericton uses wells for all of its municipal water and has been chasing EVERYTHING out of the city that even in the worst case, cannot pollute the watertable. What is stupid is that if it was such a threat, then it would be outlawed even at the rural level as we all have our own wells.

As to why Fredericton is so backwards, that discussion/rant could go on for days. I am, needless to say, glad I do not live in the city limits and do not pay city taxes.