Yet another silly renewable energy project - Page 1
Forum section: electronics / general

author: station240
author_rank: Unknown
timestamp: February 01, 2016, 07:26:55 am
content: https://www.kickstarter.com/projects/1966630940/solar-water-pump-system-with-hydro-electric-optionWas sort of pondering if these was a workable solution till I got to the part about the coffee maker and percolating water.So if you have hot water foaming out the top, how exactly do you get the cold water into the bottom.Dunno why he didn't just bolt a steam turbine to a water pump, and skip the extra plumbing at the top.At least this one doesn't come across as an obvious scam, though asking for $3m is just loopy.

author: Xenoamor
author_rank: Regular Contributor
timestamp: February 01, 2016, 01:12:09 pm
content: Storing electricity in the form of gravitational potential isn't that crazy but it's certainly not efficient. Seems like a huge waste of solar energy which is already very expensive.$3m for showing some google sketch-up drawings :L

author: digsys
author_rank: Unknown
timestamp: February 01, 2016, 01:31:53 pm
content: $100 pledged of $3 million with 4 days to go !! I think he's going to make it !!

author: fubar.gr
author_rank: Unknown
timestamp: February 02, 2016, 06:32:35 pm
content: Pumping water uphills is already done by the power companies:https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity

author: Refrigerator
author_rank: Super Contributor
timestamp: February 06, 2016, 09:21:40 pm
content: Quote from: fubar.gr on February 02, 2016, 06:32:35 pmYup, already done in my country, i saw it in a textbook although can't remember what it's called.

author: Kelbit
author_rank: Regular Contributor
timestamp: February 06, 2016, 10:47:22 pm
content: His solar idea is pretty dumb, but this does raise the interesting question of "is running my own pumped-storage facility on my property profitable." I think probably not, but hey, let's do a quick Fermi estimate.Let's assume you have a big property up in the mountains with a cliff that overlooks a lake. The lake provides a handy reservoir to draw water from and dump water into.Say at the top of your property you have a flat section of land that you're not using - call it one acre. Let's say that you can "easily" excavate this acre 1.5 meters deep to make a storage pond with a regular excavator. Now let's say the vertical distance from the bottom of your storage pond to the top of the lake is pretty big - 10 meters.The maximum volume of water you can store is 1 acre * 1.5 meters = 6070 m^3.Potential energy = mass*gravity*height = volume of water * density of water * gravity * height = 6070 m^3 * 1000 kg/m^2 * 9.8 m/s^2 * 10m = 596 MJ = 166 kWh.Okay, now here comes the really variable part - price of electricity. I'm going to make the assumption that Ontario is fairly representative when it comes to time-of-use pricing.From the Hydro One website, we can see that the on-peak price is 17.5 cents per kWh, the mid-peak price is 12.8 cents, and the off-peak price is 8.3 cents. Since Ontario has some weird rules about what is off peak and what isn't (changes due to day of week and season), let's just make a blanket statement that for our hypothetical mountain utility we can assume we're "on-peak" for eight hours a day at 16 cents and "off-peak" for 16 hours a day at 8 cents, a nice 2:1 ratio.The strategy here is to pump water into our reservoir during off-peak and drain it through a turbine during on-peak. Let's say that our pump-turbine has an efficiency of 87% for both pumping and generation (this is a pretty reasonable number for a real-world turbine once all the hydraulic, mechanical, and electrical losses are considered). Round trip efficiency is then (0.87)^2 = 76%.That means that to put 166 kWh into our reservoir, we actually need 166/0.87 = 191 kWh, which we purchase off-peak for $14.48. When peak rolls around, that 166 kWh can be converted to 166*0.87 = 144 kWh back into the grid, which we sell for $23.04. Each day, we profit $23.04 - $14.48 = $8.96.So, we make a little less than ten bucks a day, or around $3500 a year. Not a whole lot of cash, but hey, this thing's automated. What kind of pump-turbine do we need to accomplish that?The hydro equation says that power = eta*Q*rho*g*h, where eta is the machine efficiency, Q is the flow rate, rho is the density of water, g is gravity, and h is the hydraulic head. We need to be able to output 144 kWh in 8 hours, which means the machine's power peak output is 144/8 = 18 kW. Substituting and solving for flow rate gives Q = 0.21 m^3/s, or 210 litres/sec.That's a pretty big pump-turbine for a small operation. I don't know how much a unit like that would go for, or even if they're available on the open market - you'd likely have to convert a Francis turbine to a pump-turbine.Considering how small your return is, however, I think that between the cost of the pump-turbine, civil works, and engineering, this thing is a huge money-loser. There's a reason pumped storage facilities tend to be really big and use existing reservoirs - it's the only way to make them economically feasible.