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I don’t think solar powered irrigation is practical. To water 10 acres of orchard in northern California, where our water levels are “good” (wells are 100-150

by blendo 3y ago

I don’t think solar powered irrigation is practical. To water 10 acres of orchard in northern California, where our water levels are “good” (wells are 100-150 ft deep), we need about a 25 hp (20 kW) well pump. That’s ~2 kW per acre. A typical irrigation cycle is on the order of 10-20 hours. So budget about 20-40 kWh/acre for a cycle, and repeat every 10 days or so (crops need to dry out between waterings else disease spreads.) In theory, a kW of solar panels charging a 20 kWh battery for 10 days should work to water 1 acre for an entire summer season, at a capital cost of a wildly uneconomic cost of perhaps $20,000 per acre. These are my wild guesstimates informed by some orchard experience, but please correct me if my numbers seem badly amiss. ps: With PG&E power, we currently pay about $400/acre, per year.

20after4 3y ago
There are no batteries involved with the type of solar pumps the article is talking about. They are likely 3 phase pumps powered by variable frequency inverters. The inverters are similar to the VFD¹ motor drives commonly used with industrial machines. I'm not sure where you came up with a $20,000 cost estimate but it's likely a lot less than that. Particularly if you buy the cheapest stuff direct from China, avoiding avoid the dealers/installers who are probably marking up the equipment by more than 100%. Solar panels and the associated electronics have drastically dropped in price for the past several years. It should be possible to get 200 watt panels for $50-100 (or maybe even less if you buy a lot of them) That's something like $250-$500 per kW of panels. Make it $1000/kW to cover mounting hardware and wiring. The pumps / inverters are maybe a few thousand for a fairly large system. I'd say the total should come closer to $5,000-$7,000 per acre based on the power requirements you specified. [1]. https://en.wikipedia.org/wiki/Variable-frequency_drive https://en.wikipedia.org/wiki/Variable-frequency_drive

by blendo 3y ago

20after4 3y ago

There are no batteries involved with the type of solar pumps the article is talking about. They are likely 3 phase pumps powered by variable frequency inverters. The inverters are similar to the VFD¹ motor drives commonly used with industrial machines. I'm not sure where you came up with a $20,000 cost estimate but it's likely a lot less than that. Particularly if you buy the cheapest stuff direct from China, avoiding avoid the dealers/installers who are probably marking up the equipment by more than 100%. Solar panels and the associated electronics have drastically dropped in price for the past several years. It should be possible to get 200 watt panels for $50-100 (or maybe even less if you buy a lot of them) That's something like $250-$500 per kW of panels. Make it $1000/kW to cover mounting hardware and wiring. The pumps / inverters are maybe a few thousand for a fairly large system. I'd say the total should come closer to $5,000-$7,000 per acre based on the power requirements you specified. [1]. https://en.wikipedia.org/wiki/Variable-frequency_drive https://en.wikipedia.org/wiki/Variable-frequency_drive