We have wanted to put in solar power at our house for years. When I designed the house, I made sure we had close to the optimum roof pitch to maximize solar power production and we sited the house to do the same. We just don't have the money to put in a system and the ROI is iffy.
What the government gives they can take away. Spain USED to have very substantial subsidies for installing solar panels, but then the government got into financial troubles and they ended the subsidies. Fair enough. What was not fair, is that the Spanish government started to tax the solar panel installations at a high enough rate that people removed the panels....
NC has had many different subsidies and regulations over the years for solar. Years ago, I went to a solar power class at the community college, and the one big take away for me was to NOT try to sell your power back to the grid in NC. The regulations and payment scheme just did not make it easy to sell the power back to the grid. The design point for a solar power system in my area of NC, was/is to figure out your power usage, and build a system so that you do not over produce power to sell to the power company.
I think it was last year that a new bill regarding solar power was passed into NC law. The bill at one point was 50 pages long.
The bill passed into law was 10 pages.
There was an article recently about solar power systems in NC and they were saying the ROI went from 10 years to 20 because of the new law. What is odd, is that the solar power people were part of the creation of the bill and law.
The problem with the Teslsa Power wall, and similar installations, is that the last time I checked, it used lithium batteries. There are all sorts of different lithium battery chemistries. My assumption is that Tesla's Power wall is using the batteries in their cars. These batteries can catch fire and are very difficult to put out. It is not likely, but if one had a "lithium" power wall catch fire, you are going to loose the house. There are "lithium" batteries called LiFePo(Lithium Iron Phosphate) that are used in boat and RV installations that are very safe. I have never read of a LiFePo battery catching fire even though there are videos of the batteries being abused and tossed into a fire. I have seen a video of a lab test of a very large LiFePo battery installation that was on fire as a lab experiment but that is the outlier. LiFePo batteries do not have the energy density of a lithium car battery but the LiFePo batteries are being used in applications were maximum energy density is required.
You have to be careful with buying lithium batteries, including LiFePo. The "drop in" LiFePo batteries are problematic so beware. Victron and MasterVolt sell LiFePo batteries, chargers, inverters, etc., that one needs for an off the grid or grid tied system. Note, you can't just take a battery charger for lead acid and try to charge a "lithium" battery, if you do, most likely you will kill the battery. One can buy equipment from MasterVolt or Victron to setup a PV and battery system and not get locked into a single company solution. The last time I read up on the Tesla Powerwall, it could only be charged from solar or from the grid. If you needed to recharge the PowerWall with a generator you were SOL. With a system from Victron or Mastervolt, charging from wind, solar, the grid, or a generator is easily done. It is not uncommon to have boats that are charging battery systems with wind, solar, the grid, generators and alternator(s).
The big problem in all of this is cost, and while prices have really dropped over the years, even at solar panels and batteries costing around $1 per watt hour, a system is still expensive. Our average power usage year round is about 45 KW per day. It is higher in the winter and summer due to HVAC use and in the 30's during spring and fall. We get a bit more than five hours of maximum solar production a day at my latitude during the summer a bit under five hours during the winter. The rule of thumb is that you will get 77% of the solar power generated on the roof at your power outlet. Soooo, if we put up 10,000 watt hours of panels on our roof , we would generated 50KW per day but get 38.5KW at the outlets. This would likely keep us from overproducing power and giving free power to the power company.
However, if it costs us $2 per watt hour to buy and install the solar panel system, and I think $2 would be on the cheap side, that is $20,000. Batteries, chargers and inverters are even more. My guess, and it is just a guess, is that if we wanted to run just some lights, fridge, freezer, hot plate, hot water kettle and the well pump we would need around $25,000 of LiFePo batteries based on the number of amp hours needed to run the well. Batteries are limited by the number of amp hours they can produce. LiFePo is much better than lead acid in this regards but one still has to be mindful of the number amp hours one is pulling from the batteries other wise one degrades the usable lifetime of the battery.
Even if we the battery cost was $15K, that still does not cover the inverters, chargers, etc., so I think a decent PV system, with batteries, would cost $40K at a minimum. Having said that, this might be something we will have to spend as the grid because less reliable as states move from a diversity of continuous power production to single source of energy, aka, natural gas. Not to mention the price increases that will happen as is already happening in Europe. The loss of continuous power production in New York City is likely to lead to rolling black outs in the next few years if they have temps in the upper 90s... The Wall Street Journal had a report on all of this recently, here is quote about MISO cutting power production by 13 gigawatts but only building replacements of 8 gigawatts. By 2024. It is 2022... I would guess that power usage in those states is NOT going to decrease.
Within the footprint of the Midcontinent Independent System Operator, or MISO, which oversees a large regional grid spanning from Louisiana to Manitoba, Canada, coal- and gas-fired power plants supplying more than 13 gigawatts of power are expected to close by 2024 as a result of economic pressures, as well as efforts by some utilities to shift more quickly to renewables to address climate change. Meanwhile, only 8 gigawatts of replacement supplies are under development in the area. Unless more is done to close the gap, MISO could see a capacity shortfall, NERC said. MISO said it is aware of this potential discrepancy but declined to comment on the reasons for it.
Later,
Dan
