Asked Questions |
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Q: Would you consider this project a long term success?
A: In a word yes. It has saved about half on the expected energy usage for this house over a period of 20 years. It has done so with minimal maintenance requirements. Most of what has been done was in order to simply test various concepts in a real world situation. Some have been integrated where appropriate; others have been dismissed as not worth doing.
Q: Why do you not generate electricity with your system?
A: It has not proven to be a cost effective option at this point in time. The high cost of photovoltaic cells compared to the amount of power generated simply does not make it worth while when it is compared to the cost of commercial power. Maybe at some future time when the price of the panels comes down or the cost per kilowatt-hour of commercial power continues to increase this will be an option. But for now, except where commercial power is either not available or extremely unreliable, solar electric just doesn't make economic sense.
Q: Why the electric furnace instead of a heat pump? I thought they were much more efficient.
A: They are more efficient. But one need also consider the initial cost. Current units are about 3 times better than resistive heat furnaces. But again the initial cost is about $1200 more than the resistive furnace. Plus in order for the solar system to work in conjunction with a heat pump, modifications would need to be made. These adaptations would also be more involved than those needed to simply replace the sequencers in the electric furnace adding to the cost. But one of the biggest drawbacks is actually a benefit of the solar heat system. Because half of the heat demands are provided by solar, any benefit gained by using a more efficient backup heat system is only half what the average homeowner might expect. This fact alone would double the payback time the heat pump might offer.
However recent innovations, such as geothermal heat pumps and improved performance at lower cost by today's models against what was state of the art a few years ago may at some point in the future make a decision to convert prudent.
Q: Why are you using forced air instead of liquid collectors?
A: At the time the system was installed it was the easiest and most cost effective. Since then I have experimented with liquid collectors on the Water Heater and am actually considering changing to a liquid collector with a liquid to air heat exchanger in the storage unit. The double glazed collector has proven to operate much more efficiently in extreme weather than a single glazed FRP panel.
However there are good points and bad about both methods. The forced air system is not subject to leaks or freezing. It responds faster to broken cloud conditions since there is not as much mass to heat. Heat transfer is easier since the rest of the system is forced air no heat exchanger is necessary. The liquid system has the advantages of needing no large heat ducts, or large collector blowers. Plus, since water is heavier than air the problem of fighting the tendency of hot air to rise in order to force it to the basement storage is not a consideration. Pumps can move more BTU per hour more efficiently than blowers so transfer of heat to storage is better. So in reality it is a trade-off each has its good points and bad.
Q: Why did you use a custom built controller rather than a PC?
A: Since this system is one of several which operate my house I wanted to stay with the same general concept. Certainly I could have done it with a regular PC, but since the controller has only one basic duty the versatility of a PC was not an issue. Speed and memory size are also not large so the use of a PC would have been overkill. Besides that the concept was developed in the early 1980s, before PCs were found in every home. Back then even a small computer was expensive, well over $1000. So what I did was develop a small general purpose controller based around the then current 8 bit 8085 processor. I built several of them and incorporated them into various functions in my house. Since then, and to maintain compatibility between systems I have continued to use the same basic controllers. Old, primitive by today's standards, but it still works very well. There would be no advantage to re-inventing the wheel.
Q: How can I obtain information or plans to build a solar heat system of my own?
A: At the conclusion of the Frequently Asked Questions there is a list of information packets available for purchase. Decide which one suits your needs and click the link to e-mail me. I will respond with instructions to get what you need shipped to you.
Q: Can you help me design a system for my house?
A: Unfortunately there is not a lot I can do from here. I don't have your climatic information and other very important bits of information I would need to size a system to your specific needs. All I can do is what is done here, that is give you what has worked for me. It will be up to you to take what is provided, consider your situation, and make adaptations to make it work for you.
I hope this has answered a few of your questions about my system. If you have any other comments or questions feel free to e-mail me using the E-Mail link at the top of this website. I will respond to any general questions you may have.
