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I worked on solar thermal for a while. It was even mandatory to install in new buildings in my country for a while (before all solar was forbidden for personal

I worked on solar thermal for a while. It was even mandatory to install in new buildings in my country for a while (before all solar was forbidden for personal use until recently, don't ask, I hated it too. Forced me to become a sysadmin though, which was a good move). You can get pretty good efficiency with solar thermal panels and indeed they are more near the 70% mark. Just a "black paint" panel can get "decent" results and it's relatively cheap. I remember back in the training days, our teacher just held a metal pane, painted black, into the sun for a demonstration. And got to 80ºC in a few minutes. In January. They are not so useless in summer depending on where you live. In my region, despite being tropical-tier hot, water comes out really cold from the urban lines, so you always need to use some gas for a heater (butane or city gas). Having a solar thermal setup completely nullifies that (admittedly not large, but existing) expense during summer and reduces it during winter. Since many buildings here already have it as a feature, it's a little expense reduction which is always welcomed. I miss working on that field.

kQq9oHeAz6wLLS 3y ago
> I remember back in the training days, our teacher just held a metal pane, painted black, into the sun for a demonstration. And got to 80ºC in a few minutes. In January. A bit off topic and slightly different tech, but I have a solar kettle which uses reflected sunlight and boils a liter of water in a bit over an hour. The sun has energy to spare, and I always like learning new was to utilize it.
hattmall 3y ago
Isn't there some way to generate electricity from temperature differential? It seems like solar thermal and ground source water could be an avenue for that.
- abdullahkhalids 3y ago
  My undergrad thesis was about modeling a home-sized solar-thermal to electricity setup. The answer was (1) you could barely eek out something of value if you really tried (2) it would be beaten by solar panels hands down. The problem is that electricity production is dependent on the difference in temperature between your hot liquid and the environment. And the 70C-30C with water you will get in the summer is simply not enough to produce much. Realistically, you need ten times this difference to do anything useful. The other option is to heat oil, with lower heat capacity. That you could heat to a bit higher temperatures, but then you are going to continuously lose oil that has to be topped up. Unfortunately, despite my dreams, such systems seem economically unrealistic.
Scoundreller 3y ago
Which country banned solar for personal use?
- esarbe 3y ago
  Spain? https://www.pv-magazine.com/2015/10/09/spains-government-approves-the-sun-tax_100021485/ https://www.pv-magazine.com/2015/10/09/spains-government-app... The tax was repealed in 2019, but still.

kQq9oHeAz6wLLS 3y ago

> I remember back in the training days, our teacher just held a metal pane, painted black, into the sun for a demonstration. And got to 80ºC in a few minutes. In January. A bit off topic and slightly different tech, but I have a solar kettle which uses reflected sunlight and boils a liter of water in a bit over an hour. The sun has energy to spare, and I always like learning new was to utilize it.

hattmall 3y ago

Isn't there some way to generate electricity from temperature differential? It seems like solar thermal and ground source water could be an avenue for that.

abdullahkhalids 3y ago
My undergrad thesis was about modeling a home-sized solar-thermal to electricity setup. The answer was (1) you could barely eek out something of value if you really tried (2) it would be beaten by solar panels hands down. The problem is that electricity production is dependent on the difference in temperature between your hot liquid and the environment. And the 70C-30C with water you will get in the summer is simply not enough to produce much. Realistically, you need ten times this difference to do anything useful. The other option is to heat oil, with lower heat capacity. That you could heat to a bit higher temperatures, but then you are going to continuously lose oil that has to be topped up. Unfortunately, despite my dreams, such systems seem economically unrealistic.

Scoundreller 3y ago

Which country banned solar for personal use?

esarbe 3y ago
Spain? https://www.pv-magazine.com/2015/10/09/spains-government-approves-the-sun-tax_100021485/ https://www.pv-magazine.com/2015/10/09/spains-government-app... The tax was repealed in 2019, but still.