3 ms·

That still requires a heat differential to produce electricity, and thus works worse in the heat. (of course, having more intense sunlight will help make up for

That still requires a heat differential to produce electricity, and thus works worse in the heat. (of course, having more intense sunlight will help make up for the loss in conversion efficiency)

altcognito 13y ago
Not sure that this is accurate, isn't the "work" in a boiler done by the phase transition to steam and the associated increase in pressure? Unless you're referring to a particular design of solar energy production.
- ndonnellan 13y ago
  There is no associated increase in pressure in the boiler typically. In fact, there's usually a pressure drop. The high pressure is created in the feedwater pumps for a steam system. The boiler converts liquid at high pressure to steam at high pressure. The steam volume then expands to perform work in a turbine. A salt-plant would probably use steam near 100bar and expand it through the turbine to below 1 bar (sub-ambient) such that the saturation temperature is as close to ambient temperature as possible. There is a significant amount of work done at the last stages of the turbine (when going from +1bar -> 0.1 bar) so increasing the ambient temperature can have a noticeable on total cycle efficiency.
Turing_Machine 13y ago
"thus works worse in the heat" Yep, but that shouldn't be a big factor in the temperature ranges under discussion. A mirror-based concentrator can reach 3,500 C (let's say 3,700 K, roughly, though it's closer to 3,800). That's the hot side. The cold side might be about 60 C at the most (the highest temperature recorded in the Sahara appears to be 57.7 C) or about 330 K. Compare to a temperate zone setup operating at say 20 C on the cold side (say, 300 K). The first will have a maximum Carnot efficiency of 1 - 330/3700 = about 0.91, while the second will have 1- 300/3700 = about 0.92. As you say, the more intense sunlight (and especially the lack of rainy days) will more than make up for this.

That still requires a heat differential to produce electricity, and thus works worse in the heat. (of course, having more intense sunlight will help make up for the loss in conversion efficiency)

altcognito 13y ago

Not sure that this is accurate, isn't the "work" in a boiler done by the phase transition to steam and the associated increase in pressure? Unless you're referring to a particular design of solar energy production.

ndonnellan 13y ago
There is no associated increase in pressure in the boiler typically. In fact, there's usually a pressure drop. The high pressure is created in the feedwater pumps for a steam system. The boiler converts liquid at high pressure to steam at high pressure. The steam volume then expands to perform work in a turbine. A salt-plant would probably use steam near 100bar and expand it through the turbine to below 1 bar (sub-ambient) such that the saturation temperature is as close to ambient temperature as possible. There is a significant amount of work done at the last stages of the turbine (when going from +1bar -> 0.1 bar) so increasing the ambient temperature can have a noticeable on total cycle efficiency.

Turing_Machine 13y ago

"thus works worse in the heat" Yep, but that shouldn't be a big factor in the temperature ranges under discussion. A mirror-based concentrator can reach 3,500 C (let's say 3,700 K, roughly, though it's closer to 3,800). That's the hot side. The cold side might be about 60 C at the most (the highest temperature recorded in the Sahara appears to be 57.7 C) or about 330 K. Compare to a temperate zone setup operating at say 20 C on the cold side (say, 300 K). The first will have a maximum Carnot efficiency of 1 - 330/3700 = about 0.91, while the second will have 1- 300/3700 = about 0.92. As you say, the more intense sunlight (and especially the lack of rainy days) will more than make up for this.