Although sunlight is renewable, photovoltaic panels aren’t.
PV isn’t ready yet. NREL (National Renewable Energy Lab) lists the technical barriers below in: PV Roadmap. U.S. Dept of Energy National Center for Photovoltaics.
- Lack of widespread availability of low-cost feedstock and packaging materials
- Performance and manufacturing costs of high-efficiency silicon, thin-film, and concentrator cells and modules
- Improved reliability of modules and, especially, of balance-of-systems components
- Lack of standard products, packages, and service offerings
- Need for Manufacturing Center of Excellence
- Lack of knowledge of high-throughput processes
- Lack of standard module electrical/ mechanical “interfaces”
Photovoltaic (PV) performance in the real world is often much less than what the manufacturer claims. There are losses due to:
- Panels accumulate dust.
- In winter, the angle of the sun in winter is lower, so sunlight has to travel a greater distance through the atmosphere.
- The further north you go the more solar power diminishes.
- The air is often clogged with dust, pollution, or water vapor.
- PV takes a beating under the sun all day, the thin-film variety, which it’s possible to produce in large quantities, and efficiency declines, producing less electricity.
Large-scale solar PV farms need to be located in desert areas, where there’s very little water to rinse off the dust that accumulates. In 2013 the world’s largest solar-thermal plant will open, and it will need 600 acre-feet of groundwater to wash off dust and cool auxiliary equipment. Desert groundwater is not renewable. Meanwhile, sand storms will scour the surfaces of panels and other equipment, leading to reduced power and efficiency.
The amount of energy embodied in the full solar structure is far more than PV panels. It’s the energy required to build the PV manufacturing plant, to mine and deliver the silicon and copper, solar tracking systems, aluminum frames, concrete foundations, transmission subsystems, inverters, batteries, cement platforms, cabling, transformers, control systems, storage subsystems, backup power, the energy costs of delivering the PV components to the site where they’ll be used.
“For solar power, the life cycle for solar photovoltaic systems requires the use of hazardous materials which must be minded from the earth and can contaminate areas of land when such systems break down or are destroyed, such as during hurricanes and tornados. Chemical pollution has also been noted to occur durnig the manufacturing phase of solar cells and modules”. p28 of “The Routledge Handbook of Energy Security”
Photovoltaic cells are made from silicon not pure enough to make computer chips. Computers need one of the most pure substances ever made – silicon that’s 99.9999999% pure, or “seven nines” of purity. That means if you had jars with ten million pennies, only one could be a misplaced nickel. Solar panels require less purity – “six nines”, which means you could have ten nickels. The solar industry feeds off the rejected scraps. Only a few firms make purified silicon, because these manufacturing facilities cost over two hundred million dollars and three years to build.
Tom Abate. Sep 4, 2006. Chip material shortage spooks Silicon Valley. San Francisco Chronicle.
To make silicon this pure, a lot of energy is used. Quartz rocks must be ground up and then heated to 2500 degrees Farenheit. It takes 800 kWh of electrical energy to make a 200-mm semiconductor wafer. If we assume this cell has an efficiency of 10% and don’t even count the energy to deliver it to a site or store the energy and retrieve it at 100% efficiency, it will take 145 years to produce as much energy as was used making it. (Assuming the PV cell produces an average of 20 watts per square meter of surface, and the cell is .031 square meters, which makes it capable of producing .63 watts. In one year, it can generate 5 kWh of energy).
[Huber and Mills] Peter W. Huber and Mark P. Mils, “No Limits: Energy and Technology,” (Banc of America Securities, Energy and Power Conference, New York June 19,2002)
The most efficient solar cells are made from expensive materials. No one has yet figured out how to build very efficient PV from cheap material. Cheap, thin, PV has a short lifespan as it grows less efficient while breaking down in the sun.
The direct current generated by solar cells can’t power a typical household’s appliances. First it has to be converted by an inverter to alternating current. For a home to be completely self-sufficient, a battery bank is required. Acid and hydrogen gas batters are heavy, expensive, and potentially dangerous.
A PV plant that could produce 5.5 TWh of power (what the Glen Canyon dam produces) would displace an enormous ecosystem, about 20 square miles. It requires 177,788 MT (megatons) of aluminum, 2,222,356 MT cement, 480,029 MT copper, 7,556,010 MWh of electricity, and 4,600,276 MT of steel. (S. Pacca, D. Horvath 2002 Greenhouse Gas Emissions from Building & Operating Electric Power Plants in the Upper Colorado River Basin. Env Sci & Tech /Vol 36, # 14 3194-3200)
Ted Trainer estimates that building a PV power plant would cost at least 48 times as much as building a coal power plant. 2003. Renewable Energy: What are the Limits?
If the PV panels use a tracking system to capture as much sunlight as possible as it arcs across the sky, it may not track properly, and the energy to build and to move the solar panels to track the sun must be subtracted from the energy gains.
PV for home use is still far too expensive for the average household to afford, and very complex to maintain and repair. And a PV system isn’t merely PV panels, there are many other components involved, such as Charge Controllers, Inverters, Fuse Blocks, devices to feed the power to the grid, or if it’s an off-grid system, batteries and an oil-based generator to keep the batteries from being drained. All of these products can break down, requiring maintenance or replacement, and require energy to build.
The amount of PV that can be effectively used on buildings is limited by how much of the roof faces south and whether trees shade the roof.
PV. by Mark Boberg. Jun 28, 2000
PV industry, if you’re listening, here’s the challenge: commit to building and operating a PV production facility using only PV power to do it.
1) Use your best, most efficient technology, and build 10 megawatts of PV panels. Acquire all the necessary mounts, trackers, inverters, wire, batteries, controllers, etc. We won’t even count the energy required to make all this, it’s a freebie.
2) Find the best solar site in the World and set up your system there.
3) Locate, lease, and set up the equipment necessary to construct a PV plant from scratch. Select versions of all this stuff that will run on PV electrical power (invent new versions as required – an electric backhoe comes to mind). Use a PV powered truck, train, boat to bring the equipment and raw materials to the site. The lease cost of this stuff will be charged to the future PV production of the plant on an energy basis (i.e. equivalent PV panel lifetime energy production).
4) Saw the wood, smelt the steel, burn the limestone for the cement, crush the gravel, machine the bolts, dig the dirt, etc, etc, and erect the building, all using the PV from your 10 megawatt system.
5) Locate, lease, and set up the equipment necessary to produce PV panels complete (silicon production, wafer production, panel assembly, etc.) The lease cost for this stuff will also be charged to the future PV production of the plant on an energy basis.
6) Operate the plant, the employee housing, the stores and utilities supporting the employees, all from the 10 megawatt system. Don’t forget to pay the employees in scrip redeemable in PV panels.
7) Produce PV panels until “break even”, which would be something like 10 megawatts worth (item 1) plus a bunch more (items 3, 5 and 6).
8) (Maybe) produce a bunch more “net” panels until the plant wears out. Don’t forget to subtract any panels made to replace “burnouts” in your 10 megawatt array and PV panel scrip redemptions by the employees (I’m guessing about one to three 100 watt panels per employee per week).
9) Divide the number of panels produced by the number of “breakeven” panels in item 7). If the number is say, 2.0 or more, you win. Less than 2.0, we all lose.
This isn’t really an unreasonable challenge, if PV really has what it takes to replace some significant portion of the hydrocarbon energy demand. So, how about it? Solarex? Siemens? Koyocera? Solec? Anybody?
Solar power requires too many subsidies
Todd Kiefer: Just crunched an “EIA report to Congress on energy subsidies (http://www.eia.gov/analysis/requests/subsidy/pdf/subsidy.pdf) . In 2010 wind was subsidized at 2.16 cent/kWh and solar at 3.13 cent/kWh. In 2013 (latest data available), wind was subsidized at 1.31 cent/kWh and solar at 6.36 cent/kWh. Makes it easier to see why there are solar PPAs out there for 4 cent/kWh.
Full table of subsidies normalized to units of energy delivered is below. M$ is million dollar. Quad is quadrillion BTU. BOE is barrel of oil equivalent. Subsidies do not take into account offsetting federal revenues such as fees, permits, leases, excise taxes, corporate income taxes, etc. Oil and gas generates a 2,000% return on these subsidies in federal corporate income and excise taxes alone (> $9/barrel). Then there are the taxes from the 185,000 people directly employed in the oil and gas industry. I haven’t researched coal in as much detail, but I’m sure the government gets a positive return. Non-hydro renewables, on the other hand are surely net negative.”