Solar Power in Straw Bale Homes
Many of my clients will, as we start the process of designing their straw bale homes, happily say to me, “I want to incorporate solar power into my blueprints.” Alternative sources of power is a very attractive option and I recommend it highly. Unfortunately, it does have its own complications and challenges. Let me give you some of my thoughts on this:
Solar power comes in several different ways.
First, there is ‘active’ solar gain, which uses panels to generate electricity and then transfers that electricity into the house in lieu of the house getting electricity from a conventional power grid. Secondly, there is also ‘passive’ solar gain, which utilizes South-facing windows that will convert sunshine to heat as the light passes through the glass and heats the inside of the house. And third, there is solar water heating, which pumps cold water out of the house and into a panel usually placed on the roof that heats the water then pumps the hot water back into the house. .
Active solar gain
Uses glass and other materials to generate electricity. Getting power from the sun, rather than from coal-fired, nuclear-powered or other environmentally-harmful sources, is something I hope is adopted by the entire world–and soon. Supplying electricity from the roof of your own home is a fabulous option, but it is an undeniably expensive one. The present generation of solar panels is at most 15% efficient which needs to be studied and improved upon, and though the price of the panels is currently falling it still can take many years’ worth of investment before that investment pays off and one has ‘free’ electricity. In the case of houses that are tied to the grid of a city’s power, a homeowner with active solar can pump unused electricity into their lines and possibly get a monthly reimbursement check; this makes paying for a solar system much more feasible. In off-grid situations, though, not only must one pay for the solar panels but also batteries to store the electricity–and that makes such a system even more expensive, not to mention the life of the batteries is considerably less than that of the panels.
Passive solar gain
or using glass and other materials to convert light into heat. For passive solar, I have more mixed feelings. On the one hand, there is nothing as comforting to me as sitting by a warm window in the winter and basking in the combination of light AND heat as it comes through the glass . If the light-and-heat shines onto an adobe trombe wall or a thick adobe floor it can absorb that heat and radiate it back to the house during cold winter nights. In this way passive solar gain can spread warmth throughout the house. That’s the good news. The bad news is that the glass of a window has practically no insulative value, so during the short winter’s day the window will indeed convert sun’s energy into warmth—but during the much longer winter’s night, that same window will leak a lot of heat back out of the house. There is also the complication that in many parts of the world, such as Albuquerque, where I live, one is trying to cool a house down more months of the year than one is trying to heat it up. So putting a whole series of South-facing windows in my climate may work well from, say, November to February…but during the remaining 8 months of the year the windows are pouring unwanted heat into the home. There are ways to lessen the windows’ infiltration of heat during the summer, and to minimize the windows’ nightly heat drain during the winter and in fact a whole industry to do just those things has been created. Insulated shades can be used. Increasing the roof’s overhang so in winter the sun’s rays enter the glass but in summer there is no direct sunshine on the glass, is common practice. Creating a trellis for vines, or planting a tree just outside a window, will allow the leaves to naturally shade the windows during the summer and those leaves will fall off right about the time one wants the shade gone. Or making insulated panels that can be put up against the window whenever one doesn’t need the heat is always an option.
Solar water heating
or using glass and other materials to heat water. This is usually accomplished by pumping cold water into a solar panel, letting the panel heat the water, then pumping it back down to an insulated tank that holds the hot water until needed for showers, sinks and washing machines. Other than the relatively-inexpensive installation costs of a couple pumps, a solar heater, some thermostats and some piping, I can’t think of any disadvantages to this method. Who wouldn’t want to have water that’s heated by the sun!
I am wildly enthusiastic about leaving behind old polluting ways of heating or cooling a house.
Use of solar power can change the world. But when planning your home, pay attention to the budget and to the efficiency of sun-collecting products!
What other alternative power methods are you interested in? What do you think about solar power as an alternative power source?