Cracking the Whip on Solar

[bwalendy]

I never expected that my two 24vdc / 270-watt Renogy solar panels totaling 540 watts would be enough while providing power for my 24vdc 3000-watt inverter. I had fully expected that I would need to add additional panels up to roughly 1.1k watts of solar potential before my power needs would be adequate. I also did not expect that just two 100 amp hour batteries would be enough storage for overnight use. That was before I installed the 9000btu Pioneer mini-split A/C - heat pump unit. That was indeed a game-changer.

Now I have excess power generated from the panels from 9am until 7pm in the summer. My two 100 amp-hour batteries remain at 100% fully charged during those hours (overnight they never get lower than 85% capacity). That is with the mini-split keeping the inside temperature a approximately 78 degrees Fahrenheit from roughly 10am until 7pm. The mini-split is operated in “eco mode” which is perfectly adequate for this small space that is not properly insulated as yet. All the time that the A/C is running the solar panels are developing enough power to keep the batteries at 100%, to keep my small fans running, to keep my vent fans running in ceiling fan mode, to keep my electronic equipment charged, run a microwave occasionally as well as run my 32” LED flat-screen streaming videos. The solar array simply stops developing more than approximately two-thirds of its capability as there is no place for that power to go. Seems like a waste.

So here is that challenge; how do I store more power? I could add more batteries and store more power in batteries. I really don’t see the point in that as once the batteries are at 100% the Renogy 40 amp MPPT charge controller stops significantly charging the batteries. That would be true regardless of how many batteries that I add. The charge controller simply places the batteries in “float mode” or “boost mode” or occasionally “equalization mode”. How do I store more power? I believe that I have the answer; run a 5 cubic foot freezer during the day and freeze one-gallon jugs of ice solid. The freezer would remain off at sunset and be turned back on at about 9am the next morning. If that is not enough I will buy an ice maker machine and make about 10 pounds of ice a day to fill my ice chest. Between the “block ice” that I make in the freezer and the cube ice that I might make in the ice maker, I could keep myself in smoothies indefinitely as well as run a blender and masticating juicer.

I realize that my solar panel and battery storage needs might change with the seasons but I am not so sure. I am in New Mexico at an elevation of 6500’ therefore we get plenty of sunshine in the winter albeit shorter days. The mini-split heat pump uses less power than its A/C function. I will use supplemental heat such as a small wood/pellet stove and catalytic propane heater. I will also employ solar hot water before winter that will be cycled through to keep the floors warm. The only variable here that I can see is the number of cloudy days in winter and during the monsoon season. I don’t think that is an issue as I can always bring my batteries up to a full state of charge using the 2kw inverter generator that I very rarely use.

BTW: this is all done off-grid in my homemade RV (see pic). I live full-time in the forest on dispersed camping public lands.

 

[fratermus]

how do I store more power?

I agree with the approach of consuming more rather than trying to store it:

• extra freezing/refrigeration - as you say
• cooking with electricity: crockpots, rice cookers, etc. I've been doing this to make good use of solar and reduce propane consumption.
• heating water
• pumping water
• charging devices
• running laptops or tv
• build an electric scooter or bike to accompany the Honda

 

[stienman]

If you replace your water tank(s) with 5 gallon ball lock kegs, then you can run an air compressor, compress the kegs, and you won't have to run a water pump to get water pressure. Filling an air tank with pressure would be useful, and once you have it you'd find all sorts of uses for "free" compressed air.

Hot water and frozen water are good options, as mentioned. Combine them with radiant tubing and you could heat/cool the structure to supplement your other heating/cooling.

Running a dehumidifier to collect water, then a filtration system might remove the need to fill your water tanks manually.

Likewise, you could experiment with heating to dry out your waste.

Sell your scooter and buy an electric one, and keep that topped off.

 

[bwalendy]

I agree with the approach of consuming more rather than trying to store it:

• extra freezing/refrigeration - as you say
• cooking with electricity: crockpots, rice cookers, etc. I've been doing this to make good use of solar and reduce propane consumption.
• heating water
• pumping water
• charging devices
• running laptops or tv
• build an electric scooter or bike to accompany the Honda

Except for early morning coffee or a quick breakfast on the inside induction cooktop, I cook outside during the summer months. I don't see the need to worry about propane consumption. One standard-sized propane bottle (20lb?) lasts me two to three months in the summer using my Camp Chef oven/stove that I highly recommend. Therefore I don't see propane consumption worries as a battle that I need to fight. I use a solar oven for some baking and roasting. As mentioned, I have an induction cooktop for days that it is not hot outside and I use that at about 1/2 power or much less. I do use a mini crockpot for soups and stews in winter. I cook over a rocket stove or wood/charcoal grill when I have the opportunity. The BLM and Forest Service have put the kibosh on that type of equipment due to the fire risk

Using the excess power generated by making block ice seems the way to go at this point. It is, in fact, storing energy much as one would store energy in a battery. This just happens to store that energy in terms of block ice for refrigeration. I have had several of the DC refrigerators over the years. One that was quite expensive. They do not seem to last very long before the compressors give out. My theory is that a DC compressor has to work a lot harder than an AC compressor. Not sure but I don't want to buy another one. I will simply run a $129 (on sale at Wal-Mart), 5 cubic foot deep freeze, and run it through the inverter. I think that I will be ahead. With the savings in costs over a DC compressor-based refrigerator/freezer, I could have bought a lot more solar panels to push the inverter over the years. Live and learn. I have been on and off with the nomad life since 2003, the past few years I have been full-time and will stay with it. I love the lifestyle in my retirement.

 

[bwalendy]

If you replace your water tank(s) with 5 gallon ball lock kegs, then you can run an air compressor, compress the kegs, and you won't have to run a water pump to get water pressure. Filling an air tank with pressure would be useful, and once you have it you'd find all sorts of uses for "free" compressed air.

Hot water and frozen water are good options, as mentioned. Combine them with radiant tubing and you could heat/cool the structure to supplement your other heating/cooling.

Running a dehumidifier to collect water, then a filtration system might remove the need to fill your water tanks manually.

Likewise, you could experiment with heating to dry out your waste.

Sell your scooter and buy an electric one, and keep that topped off.

I have long thought about replacing the scooter with an electric motorcycle. An electric bicycle will not serve my purposes as I need to haul other heavy items besides my heavy self. Most electric scooters that I could afford have range issues that require the purchase of additional proprietary batteries that are too expensive. The only practical option for me is an electric motorcycle which are wayyyyy out of my price range. The Honda is a 250cc which is quick and fast, has an excellent range between fill-ups, is comfortable and I can easily carry groceries or jugs of water which are a lot of weight. The Honda will cruise 70 on the highway if need be and get over 60mpg. It will out-accelerate most cars off the line up to about 30mph. It only has about 20k miles on it and that model is known to go 100k with decent maintenance zero repairs. Tires, brakes, fluid changes, and the occasional starting battery are about it. I have had it for about 18 years now and it has never given me grief. Replace that with electric? It is appealing but not practical as it would be expensive to replace it and I see many more ways to make better use of those funds. I am retired and on a fixed income so the dollars just don't come my way so easily these days in my old age. I have to make the most of what I have and spend it wisely.

 

[12VoltInstalls]

I’d start using the excess power to make something- running tools, etc transfers the power into “x” produce which gets converted to dollars to supplement the fixed income. I don’t know what your skills are, but I’d make woodworking products. Maybe you’d be good with jewelry or pies or painting. Although painting doesn’t use power lol

 

[svetz]

If you've friendly nearby neighbors perhaps a community microgrid as discussed in these threads: https://diysolarforum.com/threads/power-division-control-system-pdcs.24461

 

[bwalendy]

I’d start using the excess power to make something- running tools, etc transfers the power into “x” produce which gets converted to dollars to supplement the fixed income. I don’t know what your skills are, but I’d make woodworking products. Maybe you’d be good with jewelry or pies or painting. Although painting doesn’t use power lol

It took me a minute to grasp what you are trying to put across here and I have to say, BRILLIANT! I have quite a bit in the way of simple woodworking tools and was planning on buying a few more power tools like a jointer, bench sander, etc. I also have a very large collection of presentable oak boards from pallets that I disassembled. My idea was to use the wood to make Adirondack chairs, benches, planter boxes, and the like for myself but never really considered the concept of converting the excess electricity into a sellable product. What a great idea! It is, in fact, another way to convert one type of energy into another. Much like taking the excess current generated by the solar panels to make ice. The power is converted into a lasting resource. Thanks so much. That is exactly what I am going to do.

 

[bwalendy]

I never expected that my two 24vdc / 270-watt Renogy solar panels totaling 540 watts would be enough while providing power for my 24vdc 3000-watt inverter. I had fully expected that I would need to add additional panels up to roughly 1.1k watts of solar potential before my power needs would be adequate. I also did not expect that just two 100 amp hour batteries would be enough storage for overnight use. That was before I installed the 9000btu Pioneer mini-split A/C - heat pump unit. That was indeed a game-changer.

Now I have excess power generated from the panels from 9am until 7pm in the summer. My two 100 amp-hour batteries remain at 100% fully charged during those hours (overnight they never get lower than 85% capacity). That is with the mini-split keeping the inside temperature a approximately 78 degrees Fahrenheit from roughly 10am until 7pm. The mini-split is operated in “eco mode” which is perfectly adequate for this small space that is not properly insulated as yet. All the time that the A/C is running the solar panels are developing enough power to keep the batteries at 100%, to keep my small fans running, to keep my vent fans running in ceiling fan mode, to keep my electronic equipment charged, run a microwave occasionally as well as run my 32” LED flat-screen streaming videos. The solar array simply stops developing more than approximately two-thirds of its capability as there is no place for that power to go. Seems like a waste.

So here is that challenge; how do I store more power? I could add more batteries and store more power in batteries. I really don’t see the point in that as once the batteries are at 100% the Renogy 40 amp MPPT charge controller stops significantly charging the batteries. That would be true regardless of how many batteries that I add. The charge controller simply places the batteries in “float mode” or “boost mode” or occasionally “equalization mode”. How do I store more power? I believe that I have the answer; run a 5 cubic foot freezer during the day and freeze one-gallon jugs of ice solid. The freezer would remain off at sunset and be turned back on at about 9am the next morning. If that is not enough I will buy an ice maker machine and make about 10 pounds of ice a day to fill my ice chest. Between the “block ice” that I make in the freezer and the cube ice that I might make in the ice maker, I could keep myself in smoothies indefinitely as well as run a blender and masticating juicer.

I realize that my solar panel and battery storage needs might change with the seasons but I am not so sure. I am in New Mexico at an elevation of 6500’ therefore we get plenty of sunshine in the winter albeit shorter days. The mini-split heat pump uses less power than its A/C function. I will use supplemental heat such as a small wood/pellet stove and catalytic propane heater. I will also employ solar hot water before winter that will be cycled through to keep the floors warm. The only variable here that I can see is the number of cloudy days in winter and during the monsoon season. I don’t think that is an issue as I can always bring my batteries up to a full state of charge using the 2kw inverter generator that I very rarely use.

BTW: this is all done off-grid in my homemade RV (see pic). I live full-time in the forest on dispersed camping public lands.

Update: I bought the freezer. It cost less than one quarter of the price of a DC refrigerator and holds much more, something like four times as much. It runs at full load with everything inside that is still warm at about 80 watts. I expect that to drop to less 30 watts than when all the 8 gallons of water and other items are frozen solid. Currently my batteries are at 100% charged and the charge controller is in boost mode at 28.8 volts for the 24vdc battery bank. I have the mini split on eco mode keeping the inside at 72°. I will now go out and buy the ice cube maker. I would say that this experiment has been a grand success. Mucho power to spare with only a 540 watt Renogy poly panel array. Woo hoo!

 

[2009Bounder2020]

We have 2 ebikes that we keep on the rv, its nice to charge them with solar.

 

[12VoltInstalls]

runs at full load with everything inside that is still warm at about 80 watts. I expect that to drop to less 30 watts

Your running watts probably won’t change. How often and for how long it runs? That will probably be the “change. “

 

[efficientPV]

This is homeowner crap, not commercial. That freezer is not designed to run long hours, maybe 10 minutes every hour. There is not enough sink to the outside air. The thermal mass of the skin and motor are designed to absorb a lot of that heat and dispense it over time. Probably don't want to epoxy on aluminum fins under warranty. At least get a computer fan to blow on the motor. Efficiency drops as delta T increases.

 

[bwalendy]

This is homeowner crap, not commercial. That freezer is not designed to run long hours, maybe 10 minutes every hour. There is not enough sink to the outside air. The thermal mass of the skin and motor are designed to absorb a lot of that heat and dispense it over time. Probably don't want to epoxy on aluminum fins under warranty. At least get a computer fan to blow on the motor. Efficiency drops as delta T increases.

Point well said. To help with understanding some of the details, (the devil is always in the details)... The freezer is in the "garage half" of my aluminum van. The garage portion is very well ventilated. I have an outside vent for the freezer and 650 cfm fan pulling heat out that is ventilated from the cooler living area. Please indicate how I might improve. You can't hurt my feelings as I don't have any.

 

[efficientPV]

Just what I said, put a fan on the motor to cool the case. Not much more than a muffin fan. Not because the motor is going to burn up. That motor is a heat radiator and a sink for hot because they never expected it to run all day. I run a chest fridge and initially bringing it down to temp when I come back to camp takes all day. the manufacturer expected the freezer once down to temperature wouldn't run long or often. The cooled down motor and fridge skin was expected to be a considerable sink for the heat. They cheated on the coils and having a fan to save money. You have a hot motor in a little cubby hole. Circulating air carries away heat. My fridge only runs in the day and I store cold instead of having a big battery. I know how to squeeze a watt. I have hot water, refrigerator, dishwasher with heated dry, a large capacity washer and some medical stuff to keep me alive all from PV. I do that on just a car battery.