I know we need to put a ton of effort towards research in renewable energy, specifically solar. But when it actually becomes a viable alternative to oil, and we can ~store~ solar energy efficiently, would it be best put to use atop individual homes and buildings, or as a source of electricity for whole cities?
All good answers. Both are best as about 90% of the locations are impractical. My house and most of the houses nearby are shaded by tall trees which are removing carbon dioxide from the air. Unless you are close to the Equator, a south facing roof is important for the Northern hemisphere. A steep roof is desirable to harvest solar energy in December. Alternately, we need power plants which rarely produce electricity except in December. If you live half way to the North pole = about 45 degrees latitude, snow and ice are a problem, reducing the output of the solar panels, or concentrating solar. Chipping the ice could destroy a solar panel, and climbing on steep icey roofs of multistory buildings is dangerous until May at some locals.
Most locations have several consecutive cloudy days, occasionally. This means power plants are needed that are only operated a few days per year = a large expense, and/or HVDC = high voltage, direct current power lines, that can import power from up to 2000 kilometers away = no new funds have been appropriated to do this in the USA, yet, but they are being built in Europe.
Hurricanes throughout Florida and the states on the Gulf of Mexico. Storms mean it is not practical to put the panels a meter or more above the roof to get the optimum south facing angle as the wind loading could destroy the building, if the solar panels did not blow away. Obviously better for new construction (but we are building very little in 2011) where the extra wind loading can be designed into the building, but that could double the cost of the building without increasing the resale price. Let’s do what is reasonably practical sooner than seems prudent. Neil
Hey Zeppelin, Doug and JD are both correct, but the short answer to your question is both. One of the great things about solar power is that it is spread pretty evenly over the middle third of our globe, which happens to be where all the people are. I constantly hear arguments about the space required to collect solar power. In almost all cases, the space required to power a city is never as much as the space taken up by the rooftops of the houses already there. This might be easier to see in an example like our home. We live in a 1200 square foot (sf) home that is completely powered by the sun during the summer time. The array fits very nicely on the roof of our car port, with a little room to spare. We could do the same on any home, then you wouldn’t need any space for the solar collectors that isn’t already taken up by roofing materiels right now. The problem is photovoltiac, or solar electric panels are expensive and inefficient. This means it takes more money to make electricity from this type of panel than from other sources, and it could be done with a different solar technology using less space for the same power output. Photovoltiac panels today run in the 12 to 18 % range of efficiency, but a solar thermal plant can get up past 50%. These type plants are large, and use not just the incoming photons to make electricity, but the entire wavelength to make heat that boils water into steam, which turns an electric turbine generator. There are some concentrators of this type in the SW United States and a few other places right now, mostly experimental, but the Germans are building a better one in the Northwest corner of the Sahara Desert that will power all of Europe and use the waste by product of spent steam to create desalinated sea water for agricultural use. Google, "North African Solar Project," to read more about it.
So if we put small solar photovoltiac panels on new homes today that fed the grid, we could severly reduce our loads on the grid, which would reduce coal burning, and save money by powering more homes and businesses on our current grid without upgrading it. At the same time, we could mass produce more electricity from the sun for less money using large thermal plants as well. Both are good ideas, and they work well together. By partially unloading the grid with small arrays on each new home, we can also increase the efficiency of our existing grid, leading to even fewer losses in transmission. Wind can also help us get there, this is why there is so much investment in utility wind power today. The really great thing about using solar and wind is they are complimentary by nature. At our home for example, the wind is best in the late fall and winter, when the days are shorter and the solar array is producing less. The opposite is true in the summer. The best source of energy going forward is a diverse one. I hope this answers your question. Good luck, and take care, Rudydoo
Mass production is always more efficient and specifically for solar energy has better " batteries" than homes. Solar energy is clean and autonomous but at 15% efficiency still pretty expensive.
The conversion efficiency is greater in a large project, but when solar is cost viable which it will be within twenty years, there are significant savings to be made in transmission costs. There will be many tradeoffs to consider, not the least of which is the unsightlyness of transmission lines.
The biggest problem you have with large solar installations is finding a large area near a major population center. In many cases the town councils love the IDEA of solar energy BUT just don’t want the solar energy farm IN THEIR TOWN!
In terms of efficiency, a large solar installation is far more efficient than solar panels on everybody’s roof.
However in this case the Political decision ends up trumping the Engineering decision.