C. Letellier wrote:First off I am tired of people basically accusing the utilities of stealing. They are not. Net metering was silly from day one. When it was a few percentage points of the total it was fine as the added cost to everyone else was spread out. What net metering forgot was stranded costs beyond the cost of power and transmission losses. Every grid tie home is getting multiple benefits from being grid tie and the people with solar forget those benefits. If they don't like the cost they simply need to go off grid and eliminate them. But they will then have the battery costs, backup generation costs, loss of reliability costs etc to bear.
Now back to the question of the post storage.
I will touch on several.
1. Lets start with one already mentioned. Compressed air. It has value in the shop. You can get power hand tools for it cheaper in most cases than electric and in many cases they are more durable as well. How might this fit with permies? One of my customers bought a skid with two large air tanks on it military surplus cheap. It was something like 600 gallons capacity with a working pressure rating of something like 300. He has special trusses made building a shop so those tanks are literally built into the attic of the shop now. Now my worst air tools will cycle my 60 gallon air compressor after about 4 minutes of operation and if I stop it takes about another 4 or 5 to refill the tank. So in essence what I get is 4 minutes of 5 Hp from it. Now his tank is 10X the size of mine and holds more than twice the pressure so he could easily store 80 minutes of 5 hp. It isn't huge but it is very low loss designed properly and power in the final form it will be used in. So if you can find the right stuff to re-purpose this is very much in keeping with permies principles if you need air power. So any time I have excess power I can dump it to a small DC high pressure compressor. It also might give me the ability to put in a smaller inverter power system because I didn't need to support this high power motor. A small portable gasoline or diesel compressor could be used to make up the short fall on days when the stored air wasn't enough. If the system is built right I can add systems for cooling, heating, nitrogen, oxygen and CO2 storage to it fairly easily too. And these systems could likely be made from salvage stuff too also in keeping with permies principles. Nitrogen might give me better tire life & low oxygen storage for things like apples. Oxygen storage might run my torch. CO2 storage might let me improve growth rates in a greenhouse. If you were going to build such a system with all new materials it would be expensive and definitely not in keeping with permies principles most likely. So don't. Salvage ans work smart.
2. Hydrogen storage of power was not mentioned. Done on the cheap efficiency sucks. An electrolyser is 50% to 80% efficient Cheap buildable ones are down in the 50%-60% range. So you have lost nearly half your power before you ever store it. For storage use hydride tanks. This allows the hydrogen to basically stored in a low pressure metal sponge. Semi expensive but the big advantage is the ability to store nearly lossless for decades if needed. Then go back thru a fuel cell to get the power back. There again losses amount to another 25% of the power. So roughly 33% return on power if done with affordable storage systems.(even with expensive equipment this one only runs about 60%) Not good. But if you can capitalize on any of the hidden gains here you have more to gain. The electrolyizer produces pure oxyben so there is a possible gain. It also produces heat. At full power output the fuel cell produce high humidity hot air and if it is idling only producing a little power it is endothermic and actually cooling for some types of fuel cells. So can any of these others be economically capitalized on?
3. Now for the big one that was not mentioned. Thermal storage systems. They have the ability to greatly reduced the number of needed photovoltic panels while adding solar thermal panels that will run in lower light levels and in cloudy areas. In its simplest form it is simply a large heavily insulated storage tank in which stratification is encourage.(the one out of the alaska house example was something like 5000 gallons and insulated to R70. in this case he figured he had 2 months of hot water and household heating stored) In a more complicated version you do the chiller system out of Europe. This involves both hot and cold tanks and a small heat pump running between them. Any time you have excess power you heat one and cool the other. The hot tank does the domestic hot water and household heating needs, The cold tank serves for refrigeration primary, in some cases freezer primary and AC. After having read about these systems I think they are still missing bets. The hot side could be also be preheating the oven to say 140 degrees, providing heat for a clothes drier, providing heat for a closet that in various season did different things. In summer and early fall it is a food dehydrator, fall just after hunting season it becomes a smoker and then it spends the winter warming and drying cold weather gear. In my thinking 2 different solar thermal systems, 1 hot and 2 cold tanks. Still trying to figure out how to get all the dream functions in one affordable system.