The earlier post on whether solar gives the best bang per buck in greening our electricity ran into some opposition, as I expected. Let me consider some of the objections and issues.

As a recap, I put forward that if we are going to use our money and time to attain greener electricity, what matters is how many MWH we take off the "dirty" grid (particularly coal plant output.) I measured various ways to do that, both green generation and conservation (which do the exact same thing in terms of grid offset) and worked out their cost, the MWH they take off the grid and thus the cost per MWH. Solar PV fares poorly. Converting incandescent bulbs to fluorescent in your own home or even other people's homes fares best.

A big part of the blame lies on the fact that crystalline silicon is an expensive way to make solar cells. It is, however, quite common since many PV plants started with technology from semiconductor fabrication.

Evangelical green

One frequent objection is that purchasing expensive solar panels today encourages the market for solar panels, and in particular better solar panels. Indeed, panel makers are generally selling all they can make. Many hope that this demand will encourage financing for the companies who will deliver panels at prices that make sense and compete with other green energy.

I call this being "evangelical green." Leading by example, and through encouraging markets. While I understand the logic, I am not sure I accept the argument. * Are people who can build $1/watt (superior to grid) solar panels really not going to get funding because there is not strong demand for solar panels that cost well above grid? * How valuable is this marketing bump? Can it justify the $200/MWH higher cost of solar? * What if the money went instead into lobbying, or into investment funds targeting cheaper solar panels? * Is PV truly the right thing to encourage in this way? Might thermal-solar, wind or other forms of power be better choices?

Even if the panels are free...

I added an extra line to my spreadsheet on the cost-effectiveness of green approaches evaluating free solar panels. That is, I presumed that today's $4/watt panels (*) were free, but you still paid about $3.80 per watt for installation, grid-intertie equipment and inverters, and permits. Remarkably even free panels are worse than all the other examined methods. One hopes, of course, that free panels would cause reductions in the non-panel costs, especially permits, but this is still a remarkable observation.

(*)One commenter suggests $4.70/watt is a more accurate number. Dropping non-panel costs to $3.10 puts free PV at $121/MWH, beating the PC power supply, and perhaps the gas dryer but still losing to everything else.

If the PV industry is indeed selling all the panels it makes, and is able to get large government subsidies as well, doesn't this suggest that other promising technologies are the right thing to encourage. There may even be other technologies, like natural gas microturbines for large buildings, which are not 100% clean but are much greener than what we do now.

Another technology with much promise that gets little attention is that ancient form of solar powered lighting called the skylight. Consider that offices, warehouses and stores often have lighting on during the day while the sun shines outside. Some even have put up solar panels, which then power that lighting -- taking perhaps 2% of the light that falls on the panels and emitting it inside the building. Modern skylighting technologies can pump a vastly greater amount of that light where it is needed at lower cost. Why aren't we subsidizing that?

We can't fix the problem with just conservation

I agree with this. However, pure increases in efficiency achieve conservation but they are sacrifice-free conservation,and so never a bad idea. However, PV solar is not simply a poor buy compared to conservation, it's a poor buy compared to other forms of generation, such as solar-thermal, geothermal, large wind farms and even modern nuclear power (about which you may have other opinions, of course.)

But if your goal is to have an effect now, to spend your resources to make the world a greener place, should you not start with where you can do the most good? The answer to energy problems will come from both increased efficiency and cleaner generation, not just one of those things. What's more debatable is whether it can come from conservation through personal sacrifice.

If it's PV you want, the panels are not all of the problem

As noted, even free PV panels can't compete with other methods of going green. However, this tells us that if we want to focus on something, these other cost components might be as worth attacking, or even more attacking.

After all, all forms of local generation will require cheaper inverters and intertie, and cheaper permits in most cases. Working on those will help not only PV but other localized energy forms. For example, right now there is no way to properly use PV at all except in a large installation.

Systems that could use PV combined with grid power to replace all the DC wall warts in a house might make a big difference. In such systems, a small panel, easily self-installed with low power wiring would tie into a power supply that powered many always-on DC devices. The panel would never quite generate enough power, it would always be supplemented with a bit of grid power coming through a switched mode power supply, and full grid power at night. If this power supply was mass produced, it would allow simple panel use (replacing highly inefficient wall warts) with no costs for permits, intertie and install.

I described an early form of this idea for a solar powered PC 5 years ago, but now that I realize how inefficient all our wall warts are, it might make more sense to attack them with small solar setups than the PCs.