My post last year examining the claims made about the Invelox wind turbine has been the most-viewed article on this site, and it’s no secret that I’m a fan of wind energy, so when I started seeing information about the Solar Wind tower, I was excited to take a look.
The basic idea is this: a large hollow tower allows hot, dry air in at the top, sprays water into it, which evaporates and cools the air causing it to sink. The sinking air is forced through turbines at the bottom of the tower, both generating electricity and drawing in more hot, dry air at the top. Some of the power generated is used to pump the water up the tower.
On to the claims. Compared to Invelox, the company’s claims are much less outlandish; in fact, they make far fewer quantitative claims (which also makes their entire business case a bit vague to me as well . . .)
- “Under the most recent design specifications, the Tower designed for a site near San Luis, Arizona, has a gross production capacity on an hourly basis, of up to 1,250 megawatt hours. Due to lower capacities during winter days, the average hourly output per day for sale to the grid for the entire year averages approximately 435 megawatt hours/hr.” This is a good example of a substantive claim that is apples-to-apples comparable to current electricity sources. I don’t have enough details about the tower to do a order of magnitude evaluation of the numbers, but it appears honest and transparent to give both peak and average capacity.
- “Capable of eliciting significant energy-cost savings and carbon credits. Electricity produced is priced at 1/3 that of other alternative energy sources.” Ruh roh–you have to be specific! Which other alternative energy sources? What prices are you using for comparison? And why can’t you come out and give a projected price in $/kwh rather than merely comparing to “other” sources?
- “Capable of operating and producing energy 24 hours/day, seven days/week.” This is kind of a lame claim. The only energy source not capable of 24 hours/day production is solar-electric, and let’s be honest with ourselves here–this tower is basically a windmill that uses a clever trick to create the pressure differential. It’s only “solar” in the same sense that tidal power is “solar”–both use the effects of the sun upon the earth’s elements to turn a turbine, but are by no means directly generated power from sunlight. They have admitted that the production capacity drops in colder weather–how does this variation compare directly to that of a conventional windmill?
- This is a really cool concept, and I agree in theory that it could work. However, there are no specifications about how large the tower will be, what kind of turbines would be used, etc. In fact, there doesn’t seem to even be a working prototype of this design (at least not one they’re talking about or showing). How do they justify the cost of building the full scale thing?
Take a look: Solar Wind Energy Tower