Some of you may know already that this November we had a Geothermal Heat Pump system installed in our home. Many of you may not even know what that is (I didn’t either until oil prices skyrocketed last year and I started looking for an alternate heat source) and may be wondering why a new HVAC system justifies a blog. Most people don’t even think about their heating and cooling systems, they just set the thermostat, hope that everything works right, and have a heart attack when the bill comes. We fell into that category up until a few months ago as well. Turns out that there’s a lot of different heating and cooling systems out there, and hopefully this blog will be insightful even for those people who really don’t think it’s something they need to know about.
Until recently, our house has been heated in the winter by a 50-year-old oil boiler feeding baseboard-radiating heat. This boiler also provided our domestic hot water (at the scalding hot temperature of 180 °F). We did not have central air conditioning, so in the summers we cooled the house with window AC units. During the peak heating season we generally got our oil tank filled every 1½ months for about 150 gallons of oil. Our price was locked at $2.49/gal, so we averaged $249/month in oil expenditures. Enter the spring of 2008 when oil prices skyrocketed to over $4.00/gal and our oil company decided to fill us when we really didn’t need it in June (they can do that unless you explicitly tell them not to) at close to max price of $4.79/gal. Total bill: $763.67. To be paid all at once. How’s that for a kick between the legs? After singing soprano for a few weeks and narrowly avoiding going postal, I finally regained my sanity and began searching for an alternative source of heat.
I looked into all sorts of different heating options, learned a lot in the process, and ultimately discovered Geothermal Heat Pumps. Turns out Geothermal Heat Pumps (hereafter referred to as GHPs) have been around for quite a while, but they have only been gaining popularity very recently. To really explain what a GHP is, I should start by explaining heat pumps in general. Heat pumps work off of the relatively basic principal that any substance, no matter how cold it is, has some sort of heat energy in it (i.e. unless the substance is at the temperature of absolute zero, it’s molecules have some energy and are moving around, bouncing off of each other). A heat pump is a machine that transfers heat energy from one substance to another, most commonly by using one or a series of compressors. Traditionally, the term Heat Pump is used to refer to the more traditional Air Source Heat Pumps (ASHPs), which are quite common. ASHPs are widely used in residential applications and they work by sucking the heat energy out of the outside air and transferring it to the inside air. The great thing about heat pumps is that they can run in reverse, and so they provide heating in the winter and cooling in the summer. The problem with the traditional ASHP is that air temperatures change a great deal during the year, and as air gets really cold in the winter, the heat exchange becomes very difficult and inefficient. In fact, most ASHPs cannot effectively transfer heat on the coldest days and require a fossil-fuel or electric resistance heat backup system, thus effectively destroying their efficiency, especially in northern climates (anywhere the temperature remains consistently below 40 °F for long periods of time in the winter).
Until recently, our house has been heated in the winter by a 50-year-old oil boiler feeding baseboard-radiating heat. This boiler also provided our domestic hot water (at the scalding hot temperature of 180 °F). We did not have central air conditioning, so in the summers we cooled the house with window AC units. During the peak heating season we generally got our oil tank filled every 1½ months for about 150 gallons of oil. Our price was locked at $2.49/gal, so we averaged $249/month in oil expenditures. Enter the spring of 2008 when oil prices skyrocketed to over $4.00/gal and our oil company decided to fill us when we really didn’t need it in June (they can do that unless you explicitly tell them not to) at close to max price of $4.79/gal. Total bill: $763.67. To be paid all at once. How’s that for a kick between the legs? After singing soprano for a few weeks and narrowly avoiding going postal, I finally regained my sanity and began searching for an alternative source of heat.
I looked into all sorts of different heating options, learned a lot in the process, and ultimately discovered Geothermal Heat Pumps. Turns out Geothermal Heat Pumps (hereafter referred to as GHPs) have been around for quite a while, but they have only been gaining popularity very recently. To really explain what a GHP is, I should start by explaining heat pumps in general. Heat pumps work off of the relatively basic principal that any substance, no matter how cold it is, has some sort of heat energy in it (i.e. unless the substance is at the temperature of absolute zero, it’s molecules have some energy and are moving around, bouncing off of each other). A heat pump is a machine that transfers heat energy from one substance to another, most commonly by using one or a series of compressors. Traditionally, the term Heat Pump is used to refer to the more traditional Air Source Heat Pumps (ASHPs), which are quite common. ASHPs are widely used in residential applications and they work by sucking the heat energy out of the outside air and transferring it to the inside air. The great thing about heat pumps is that they can run in reverse, and so they provide heating in the winter and cooling in the summer. The problem with the traditional ASHP is that air temperatures change a great deal during the year, and as air gets really cold in the winter, the heat exchange becomes very difficult and inefficient. In fact, most ASHPs cannot effectively transfer heat on the coldest days and require a fossil-fuel or electric resistance heat backup system, thus effectively destroying their efficiency, especially in northern climates (anywhere the temperature remains consistently below 40 °F for long periods of time in the winter).
Enter the GHP. Geothermal Heat Pumps can work a number of ways, the most common of which is a water-source system (which is what we had installed). With a GHP, a line of pipes is buried underground on your property, preferably below 6 feet. In our case, we had three 200 foot wells drilled in our backyard, and the lines run out of our house and down into those wells, then loop back around into the house. At that depth, the ground temperature typically remains between 40 and 55 °F all year long. A water/antifreeze mixture is circulated through the pipes and enters the house at ground temperature. The GHP transfers heat energy from the water/anti-freeze solution to the air in your house and sends the cold solution back into the piping field where the ground’s constant temperature heats the solution back up again and the process continues. Essentially, a GHP uses the constant temperature of the earth as a heat source in heating mode, and as a heat sink in cooling mode. This makes GHPs significantly more efficient than their traditional ASHP counterparts, and ridiculously more efficient (and cleaner) than any form of fossil fuel. See my mathematical illustration below:
Our Old Oil Boiler at 79% efficiency:
1 gallon of fuel oil contains 138,500 BTU’s of heat energy.
At 79% efficiency, 1 gallon of fuel oil produces 109,415 BTU’s of heat
At the max heating oil price of $4.79/gallon, our price per million BTU’s of heat would be: $43.78
At today’s current low oil prices of around $2.00/gallon, our price per million BTU’s of heat would be: $18.28
Our New Geothermal Heat Pump System:
1 Kwh of electricity produces 3,412 BTU of heat energy with standard electric resistance heat.
Our Old Oil Boiler at 79% efficiency:
1 gallon of fuel oil contains 138,500 BTU’s of heat energy.
At 79% efficiency, 1 gallon of fuel oil produces 109,415 BTU’s of heat
At the max heating oil price of $4.79/gallon, our price per million BTU’s of heat would be: $43.78
At today’s current low oil prices of around $2.00/gallon, our price per million BTU’s of heat would be: $18.28
Our New Geothermal Heat Pump System:
1 Kwh of electricity produces 3,412 BTU of heat energy with standard electric resistance heat.
1 Kwh of electricity produces 15,354 BTU of heat with our Climatemaster Tranquility 27 Geothermal Heat pump operating at max efficiency of 4.5 COP.
At our current electricity price of 10.64 cents per Kwh our price per million BTU’s of heat is: $6.93, 38% of the cost of oil.
At our current electricity price of 10.64 cents per Kwh our price per million BTU’s of heat is: $6.93, 38% of the cost of oil.
At current oil prices the savings works out to be approximate $125.00/month during peak heating season. Obviously if oil prices rise again the savings becomes even more substantial. In addition, the GHP is significantly more efficient than an average air conditioning system. The efficiency of an air conditioning system is measured in a unit called a SEER. The SEER value of a standard air conditioner is 10. To qualify for the Energy Star rating, a high-efficiency air conditioner must have a SEER value of 13. The SEER value of our GHP is 27. While I have been writing about all of this from a strictly economic savings perspective, I should also note that our substantial decrease in energy and fossil fuel usage is also very environmentally friendly. I know this has been a really long and somewhat technical blog, but hopefully everyone who made it to the end found it informative. Now for pictures:
The well loops
Connecting the wells to the pipes from the house.
The trench from the house to the well field.
The pipes from the trench into our basement.
The pipes entering our basement wall.
The pipes connecting with the geothermal unit.
The pump system.
The Geothermal Heat Pump
(This is a Climatemaster Tranquility 27 unit that was made by Climatemaster for a company called Heatcontroller. As such, it is stamped with Heatcontroller's name and called a Geomax 2)
The Desuperheater loop.
I didn't explain this above, so I'll explain it hear. During the course of the heat transfer, a certain amount of heat energy is lost and thus wasted. This unit (and most of the major brand-name units) uses a piece of equipment called a desuperheater to collect that lost heat energy which supplements our electric water heater. Essentially, the water from the bottom of the water heater (which is the coldest) runs through the desuperheater and then gets pumped back into the hot water heater at a much higher temperature. This will save us on the hot water heater's energy usage by about 25% in heating mode and 75% in cooling mode.
The Whole Assembly
1 comment:
You guys crack me up! Very educational, enlightening, and technical. Much more desirable reading than the junk I have been seeing on facebook and myspace!
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