Heat Pumps

One of the agonies of home ownership is having to get your home heating and air conditioning systems overhauled, and sometimes replaced. In Texas AC compressors last some five to ten years. Most Texas homes use natural gas furnaces, and they are often of mediocre performance. In addition natural gas is also used to hear water, and for cooking. The long term supply of natural gas is uncertain, but significant untapped reserves cannot be ruled out. In addition enormous supplies of Natural Gas are avaliable from the Persian Gulf. There are economic reasons for prefering local energy sources to natural gas.

Burning natural gas creates greenhouse gases. This is the most significant issue with gas, and needs to be considered quite appart from other issues. The principle for energy use should be to replace carbon source energy where and when it is possible, and to make its use as efficient as possible, in situations where it cannot be replaced. Electricity and sunlight can efficiently replace natural gas. Since electricity can be generated by non carbon sources, using electricity in place of natural gas is moving toward non-carbon sourcing.

In an earlier post I pointed to the advantages of solar water heating, In most localities, solar water heaters pay for themselves over time. This appears to ne the case even in Toronto. Solar water heating can reduce household carbon footprints by 20%, and solar water heaters should be manditory for new homes.

Gas ranges can be replaced by electric ranges. Home construction standards should specify electrical stoves in all new homes.

Finally, we have the issue of heating. As I pointed out almost all homes have to air temprature control systems, a furnace for winter heat, and an air conditioner to control summer heat. Now the interesting thing about air conditioning is that their cooling cycle can be reversed. An air conditioner is basically a pumping system that moves heat around. Basically the air conditioner collects heat from inside the home, and moves it outside. The process can be reversed. It is possible to collect heat from the outside and move it inside. That is what an heat pump comes in. A heat pump is basically a reversible air conditioner that moves some heat from outside a structure to inside. But how can you get heat from cold winter air? basically by chilling it even more. Just as air conditioners are able to deliver chilled air inside during the summer, while generating hot air outside, heat pumps generate even colder winter air outside, while delivering warm air indoors. Heat pumps can deliver warm heat indoors even in sub-zero Canadian winter weather. They can also keep Texans cool during hotter than hell Texas Summer days.

There are three basic types of heat pumps, but only two of them are typically installed. The first is air-source heat pump. This is your basic air conditioner with a redesign that allows it to move hot air inside during the winter. Some of these models can be as much as 5 times more efficient as traditional electric heaters, and they are also very efficient air conditioners.

The second type of heat pump is called a geo coupled heat pump. Fluid from the system is circulated through tubing under ground. Heat is dumped into the ground in the summer, and returned to the house during the winter. Geo-coupled systems are actually more efficient than air-source systems, but they are also more expensive. In addition, the placement of significant parts of the system underground can create significant headaches, if the system needs repair. Geo-coupled systems also require more yard space since heat cannot be dispersed into a small area. Geo-coupled heat pump systems are also efficient for heating water.

Geo-coupled heat pump systems work well with commercial and industrial buildings. The underground system can, for example be placed under parking lots.

Water source heat pumps move heat back and forth from water. They are far less common and probably will continue to be.

Electrical utilities have reasons for wanting to see their customers install heat pumps instead of gas furnaces. Heat pumps increase winter electrical use. This means that generators solely devoted to summer peak power have winter uses as well. At present electrical companies use gas turbine generators to produce peak electricity. Gas is an expensive fuel for electrical generation, but the turbing generators are cheap. There are three principle drawbacks to the system. First it produces greenhouse gas. Secondly the long term price trend for natural gas is toward increasing cost. Thirdly, it is not clear how long the gas supply will last. Thus electrical companies considering the inevitable replacement of natural gas generators, want to find year round uses for new generators.

Thus electrical companies have a motive to subsidize the purchase of heat pumps by their customers. Heat pumps promote more consistent year round electrical use patterns, thus reducing the expensive necessity of maintaining power plants solely for summer use. Geo-coupled heat pumps especially lower summer air conditioning related electrical use. The lower electrical demand translates lower peak power demands, hence fewer peak power plants need to be maintained. In this case efficiency works to create a better balanced electrical system.

It is clear then that new building codes should require air-source or geothermal heat pumps, or other carbon free heating and cooling options. Electrical companies have incentives to offer rebates to customers switching to heat pumps, with higher rebates going to home owners who install geo-coupled systems. Local, state and national governments should also subsidize conversion of existing homes to heat pumps. Natural gas can be taxed to provide money for the installation of heat pumps in the homes of poorer people. The the added expense of paying taxes provide an incentive for all homeowners to switch to low carbon heating, while the government program removes the replacement cost burden from the poor.