I have been sifting through many ideas for many years, and have discarded the ones that don't make best use of my time and talents. I've pursued: collecting old examples of useful technology, trucks, tractors, engines, etc., Stirling heat engines, built 16 working variations; composting toilets, good potential with ongoing commerce, may get back to this one; light aircraft, a fun money pit; solar PV, did a few installs, expensive for the payback, but this is changing; and the one deserving more time and attention, solar water heating with the best available technology.
This is the main focus of my current endeavors. Using current sunshine is the best way to sidestep pollution in energy collection. The greatest savings in alternate energy production is in water heating, for many reasons. Water heating costs quite a bit when done with conventional means. It involves a thermal storage mass that is fairly dense and yet easily transported (pumped), charged and extracted in heat value; I.E., BTU's per (time unit). Add to this the idea that thermal energy from the suns’ radiation is a fairly efficient conversion, far more efficient than solar to electricity. Most developing or developed nations (vague terms, I know) in the world are getting this idea, but in the good old 'comfey' US of A, we are wanting to stay with our easily gotten energy use establishments, while somehow expecting an improved outcome. NOT gonna happen, kids. All across our land I've seen housing constructs, and nary a solar application among them. Perhaps the isolated example, but far, far from a movement, much less mainstream.
Over half of domestic and business energy heating needs, and they are plenty, can be accomplished easily with solar directly using current sunshine. And did I mention that water is also a good thermal storage material for the unavoidable off-sun periods. I think of the water tank as a storage battery for the same watts of energy.
My years of research into this field has drawn me to using the coaxial vacuum tube type of solar collectors. This type involves a twin wall tempered glass tube with a vacuum in between the walls to insulate the inner heat absorbing and transferring materials. It also gives a rounded face to the solar absorber that passively tracks the sun through most of the solar day. In other words, it provides the same collection surface amount facing the sun for most of the day, without moving parts. The collected heat is transfered upward to a glycol & water filled manifold that carries the heat to a storage tank for domestic hot water, (or larger tank that could be connected to space heating) with an alternate means of back up energy for those extended sunless times.
Larger systems use larger tanks with good insulation and more collectors for more energy input when available.
The main reason I have favored the glass vacuum tubes is that they perform so well in the cold times of the year, when heating is most needed for many uses. (I have experienced some of the hottest water temps in 5 degrees below zero weather.) They are also nearly transparent to the wind, and fairly light in weight for roof mounting (no special reinforcements.) The collected FREE heat can be used for whatever one may want heat for. Think of the uses beyond just in the home. Institutions, schools, hospitals, car washes, laundromats, factory processes, on and on. Once there is hot water, living and working space can be easily heated AND cooled.
The greatest hurdle in implementing solar thermal is the up front costs associated with providing the structuring of a lifetimes worth of heating energy in advance. "Pay now, Use from now on" is a concept that fuel and energy purveyors would rather we did not consider. We have gotten used to buying what we need to make increased heat energy while the sun shines on our planet with many times more energy than we could possibly use. We just need to implement ways of collection and storage that make sense, and we are well on our way to lessening our energy impact on the planet while using less of our limited assets and polluting less.
From one who knows it works, it has been an entirely worthy investment, and perhaps the main area the government could be helping in the implementation would be in providing low or no interest loans or outright credits for the purchase. If ones ongoing water heating costs could be channeled now for solar heating, the eventual costs would be laid off altogether, and pollution abatement would be happening as soon as it is installed. So, that’s why and where I put my time lately, because few others are, and it is so much needed.