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Solar Cells

Solar Cells

MIT professor Daniel G. Nocera is excited because he’s developed a way to separate hydrogen and oxygen using catalysts and electricity; It’s still no more than a lab experiment (the design requires platinum, which is very expensive, and suffers from the usual electrode erosion and low production issues.) Presuming the separation mechanism can be made other than experimentally possible, he suggests using the hydrogen and oxygen in a fuel cell centric design to recover the energy later. He’s apparently under the impression that energy storage is the problem.

Unfortunately, that isn’t the entire problem, or even a problem at all at medium to large scales.

At other than small scales, the storage problem has long been solved. On the energy storage side, during the day, we can simply use solar power to pump water uphill in a closed (non-evaporative) pair of reservoirs. On the energy generation side, 24/7, use a hydro generation scheme to retrieve power from the water running back downhill.

The benefits of this scheme include the following:

  1. The water doesn’t evaporate or otherwise “wear out”
  2. Practical hydro systems (water wheels, flow controllers and generators) require minimal maintainance (basically bearing lubrication)
  3. Generators are very efficient
  4. Water transport can be efficient (some pumps, bucket systems)
  5. System capacity is limited only by reservoir design.
  6. Energy generation and storage can operate at peak efficiency at all times, regardless of load
  7. Supply-side energy production can be closely matched to demand load
  8. “Load balancing” is integral to the system
  9. The entire system is 100% clean and environmentally friendly.

Downsides? Just one: Such a system requires considerable water storage, and therefore, a great deal of land area. Doesn’t have to waste any water, though – once set up, such a system may be closed.

Usefully, the amount energy stored is directly proportional to the amount of water storage and the height difference between the two reservoir levels, so you use hills or towers or both. The greater the distance between the two reservoirs in height, the less water required for the same amount of energy stored.

For example a 25 foot difference in height provides almost exactly 25x more storage than a 1 foot difference in height. So you need 25x less water to store the same amount of energy in the 25 foot system. At 100 feet, you need 1% of the water for the same energy storage, and so on. For any practical system height, this relationship holds true.

So we’ve had this solution for viable local storage (you could even call it time-shifting) of energy (solar or otherwise) for many years now. It’s a solved problem. Practical working examples exist in many locations, and at many scales. (Here’s the wikipedia page on pumped storage… check out the list of large-scale plants at the bottom!) While an urban setting (zoning and space issues) precludes implementing a home version, utilities can (and do) build systems designed to provide for large groups of customers. In 2000 the United States had 19.5 gigawatts of pumped storage capacity, accounting for 2.5% of baseload generating capacity.

The real problem is what it has always been and that is the lack of a maintainance free, long-lasting solar energy collection system. Solar cells wear out in about 20 years (while losing efficiency all that time) and are extremely vulnerable to damage from hail and high wind. They’re not very efficient, either. Steam systems are highly corrosive; so far, no one has shown up with a steam generator that will last very long. Turbines that can survive in a steam environment are hugely expensive, though we do know how to make them. Sterling engines are apparently too difficult to make. Solid state heat to electricity devices are beginning to appear, but we’ve no baseline on cost or longevity as yet.

What we need more than anything are inexpensive, high efficiency solar cells (or another energy collection and conversion device.) Until they show up in a catalog where we can actually buy them, we’re trying to roll a very heavy cube up a very steep hill.

Once we have them, if someone added practical ultracaps to the mix (I’m looking at you, EEStor), we’d be where we need to be for home storage.

My last electric bill was double what it was last year, same time period, same usage patterns. My utility (NorthWestern Energy) reported profits this quarter that were up 295% from the same period last year. I view these facts together in less than complementary terms.

I’m 100% ready to get off the grid; and I’ve got 1000 square feet of roof facing east and another 1000 square feet facing west in a region that is very sunny and dry (Montana.) I’ve got a lot of available space in the basement, too. As you might imagine, I watch the energy news like a starving animal watches for scraps of food.

I truly hope professor Nocera can turn his splitting system into a practical storage device we can all afford. Or that EEstor makes that ultracapacitor breakthrough. But until someone can give me a roof full of high efficiency, long-lasting solar cells at some kind of reasonable price level, it isn’t going to matter a whole lot. All I know is that the pressure to do something about it increases with every electric bill I receive. They’d better enjoy those profits while they last; gouging the customer only works just so far.