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Using excess energy to heat a thermal mass is infinitely better for the person who owns the solar panels / efficiency than piping it back into the grid, where y

Using excess energy to heat a thermal mass is infinitely better for the person who owns the solar panels / efficiency than piping it back into the grid, where you a) need more electrical work (paying an electrician to install a grid-tie inverter costs thousands and also negates your ability to use the power off-grid if you ever wanted to add batteries) and b) best case get credits that are deliberately priced next to nothing. The price of LifePo4 lithium batteries has also plummeted in recent years. Cool project though!

frankus 5y ago
You're both overgeneralizing and overstating the case here. PV is superior to solar thermal in a number of important ways, and grid-tie systems can be extremely cost-effective relative to storage. The article here https://www.greenbuildingadvisor.com/article/solar-thermal-is-really-really-dead https://www.greenbuildingadvisor.com/article/solar-thermal-i... details them, but the TL;DR is that solar thermal is only useful for when a) the sun has been shining for the last few hours and b) your household currently can use a source of (low-grade) heat. In contrast, PV can be used for all sorts of things (transportation, cooling) and can be exported to your neighbors via the electric grid. Thermal storage is also not especially space-efficient. Best-case scenario is that you can store about 100 Wh (~US 1¢) of energy per kilogram of mass, which pretty much rules out any kind of seasonal storage. Also grid-tie systems are a phenomenal deal compared to battery storage. I live in a place with a pretty favorable regulatory environment, but the net effect of my grid-tie system is that I get to rent an 8 megawatt-hour battery for around US$8 per month. A battery system like that would likely cost in the single-digit millions if I were to purchase it.
- sacred_numbers 5y ago
  I think the person you are replying to is suggesting using PV panels to heat a thermal mass (using resistive heating or possibly a DC heat pump) to avoid the expense of an inverter and other electronics necessary to connect to the grid. This is actually a pretty good idea now that PV panels are a much smaller percentage of the total cost of solar nowadays.

frankus 5y ago

You're both overgeneralizing and overstating the case here. PV is superior to solar thermal in a number of important ways, and grid-tie systems can be extremely cost-effective relative to storage. The article here https://www.greenbuildingadvisor.com/article/solar-thermal-is-really-really-dead https://www.greenbuildingadvisor.com/article/solar-thermal-i... details them, but the TL;DR is that solar thermal is only useful for when a) the sun has been shining for the last few hours and b) your household currently can use a source of (low-grade) heat. In contrast, PV can be used for all sorts of things (transportation, cooling) and can be exported to your neighbors via the electric grid. Thermal storage is also not especially space-efficient. Best-case scenario is that you can store about 100 Wh (~US 1¢) of energy per kilogram of mass, which pretty much rules out any kind of seasonal storage. Also grid-tie systems are a phenomenal deal compared to battery storage. I live in a place with a pretty favorable regulatory environment, but the net effect of my grid-tie system is that I get to rent an 8 megawatt-hour battery for around US$8 per month. A battery system like that would likely cost in the single-digit millions if I were to purchase it.

sacred_numbers 5y ago
I think the person you are replying to is suggesting using PV panels to heat a thermal mass (using resistive heating or possibly a DC heat pump) to avoid the expense of an inverter and other electronics necessary to connect to the grid. This is actually a pretty good idea now that PV panels are a much smaller percentage of the total cost of solar nowadays.