As noted in prior columns, California is moving toward Net Zero Energy (NZE) homes - homes that produce as much energy as they consume. This is primarily accomplished with very efficient homes that use little energy and have a solar electric system to offset that energy use. The all electric Daikin Altherma air-to-water heat pump is and will play a big role in getting home owners to NZE.
Do not confuse the Altherma with geo-thermal heat pumps or air-to-air heat pumps. Geo thermal certainly has its place, but often is cost prohibitive or may not be a good fit for smaller residential lots, etc. The Altherma produces hydronic heating and cooling for the home, and also hot water for showers, laundry, etc. One can also get an Altherma that produces only heating and hot water with no cooling. When combined with a solar hot water system and a solar electric system, the Altherma is a powerful package that gets homeowners to NZE.
I'll back up for a moment. As noted in prior columns, passive solar design combined with a very tight building envelope (air sealing – weather stripping, caulking, etc) and excellent insulation does make it possible to have a home that can passively heat and cool itself naturally. This can be done with little or no back-up heating or cooling provided by heat pumps, furnaces, and AC or wood stoves. There are times when site restrictions (hills, trees, etc) can limit the performance of passive solar design. Of course, there will be homeowners, builders, or developers who have priorities other than passive solar design and cannot or will not take full advantage of passive solar opportunities. Also, in many or most cases building codes will require some form of back-up heat.
This is where the Altherma will shine. It captures renewable energy from ambient air. Via its very efficient compressor and other components, it transfers heat to the home. It can work in very low temperatures and higher temperatures, essentially capturing what energy is available in the ambient air. The Altherma is a compact and quiet unit that can mount just outside the home. As a heat pump it transfers heat from outdoors to indoors for home heating and for cooling the process is reversed.
The Altherma is all electric so it eliminates the need for propane or natural gas, which many feel is a real safety factor. One of the key components is the efficiency of the inverter – per the Daikin website, "An integrated frequency converter adjusts the rotational speed of the compressor to suit the heating demand. " The system generally does not need to operate at full capacity. The system modulates up and down to deliver only what energy is needed. Daikin is a Japanese company that has been around for many years and has been a leader in compressor technology.
Ideally the heat is delivered thru a radiant floor system – warm to hot water is pumped through tubing in the floor, providing very comfortable heat via a quiet and ductless (dustless) system. One can also use low temperature radiators. The cooling is provided by delivering chilled water to fan coil units. These have small efficient fans that gently and quietly blow cool air into the room. To increase efficiency the home can have controlled zones so you are only heating and cooling the rooms that you desire. Thousands of Altherma units have been installed in Europe and Canada. Part of the reason for this is that those regions of the world utilize radiant heat more than the U.S. does; and they are by and large more energy conscious.
Designers can size a system based on square footage of a home, the R values of insulation, U value of windows etc. Load calculations are done that will determine the number of BTU's required to effectively heat and cool the home. It is possible to retrofit an Altherma package into an existing home. Building efficiency and comfort is becoming more of a science as discussed in prior columns regarding Energy Upgrade California. We have come a long way in getting to NZE.
