Excess Sun Power

[madmax]

Unfortunaltely I cannot use a window air unit. My windows all slide open sideways. I do not have double hung windows. I did look for a mini-split, but that would only cool one room, and I already have central air. So even if I have a mini split, I would still have to run the central to cool the house anyway, there would be no savings. Thanks anyway!

not exactly true. If you run the mini split to where the return air of your central air is, you reduce the return air temp which in turn, reduces the load.
I am not exactly sure how much effiicency you'd loose, but aint bad. The water heater is just the easiest of the bunch to do, but resistance water heating isn't as efficent as a heat pump water heater. There used to be a company called Glacier or something like that, that would make auxiliary add on heat pump water heating... but the company has since stopped making it.

 

[copec]

The heating/cooling model of a structure is pretty straight forward, if you are heating/cooling a room separately than the main heating/cooling is only handling the rest of the house. That shows up in it running less time and compressor load. I use a couple of portable heat pumps that I only run during the day to either put heat into the house or remove it ( https://www.amazon.com/Cooper-Hunter-Conditioner-Including-Controller/dp/B098ZTKTRZ/ )

A related side project I'm working on is to convert a 2-ton window air conditioner to move heat from one 500 gallon IBC tote to another, one chilled for AC during the summer, another for pre-heating domestic hot water and also heating during the cold seasons. I want to set it up with a raspberry pi or PLC or something so that it can either dump excess heat or gather heat from an outdoor heat exchanger when needing to. It would basically just continually run when PV is at excess to charge up heat/cold storage.

I want to integrate it with hydronic systems from https://www.mbtek.com/ or https://www.chiltrix.com/

The ideal model is to have an insulated (swimming) pool with a heat pump that either heats or cools running off solar during the day, and then either remove or pump heat into the pool for HVAC/DHW. A decent sized pool would experience an unnoticeable temperature swing between day/night cycles.

One could do this with off the shelf liquid/liquid heat pumps (ground sourced hydronic heat pump).

What I should do initially is make a simple preheat loop in a home built thermal storage tank, and just put a heating element in there.

 

[notarichman]

during winter or just cold, i use my solar to power a small space heater -- 350 watts. i checked one months electric bill and i saved
about $20...but the calculations are definitely not accurate.

 

[Repro]

I have my system pretty much at full use now. The addition of the two water heaters was what I needed. We have experimented with them and they are simply amazing. When the batteries are full, we start washing clothes, run the dishwasher... The system handles it well powering them almost totally with daylight sun power. I will admit that when both water heaters are running at the same time, they do draw some battery power as well, but they heat up very fast and the batteries top off again quickly. My brother-in-law helped me run PEX lines with a bypass from one of the water heaters to our small secondary bathroom for showering as well. It works great. We also installed a shower head with a button to turn the water on/off while showering like in our RV. Six gallons of hot water is more than enough for showering, and they heat up so fast, you never feel a drop of cold water.

Living in southwestern Pennsylvania has its disadvantages of being gray most of the time. We average 160 sunny days per year, and our solar works great. Even through the winter with short dark days, our inverter switched to grid two different times between 5 AM and 6 AM. When the sun came up, the solar charged the batteries and I have a set point of 53V to switch back from grid.

All in all, I am happy wih the two water heaters, they are saving us money, our gas bill will drop as our water heater is being used much less, and my system is using almost everything it has now. My Victron 150/70 Solar Charge Contoller gets so warm I could use it for heating as well.

 

[copec]

during winter or just cold, i use my solar to power a small space heater -- 350 watts. i checked one months electric bill and i saved
about $20...but the calculations are definitely not accurate.

My house is still basically a rigid tent. So running the portable heat pump all day during the winter on solar paid for itself in the cost of gas.

I need to just pick up a large electric water heater and put it in series before my gas heater.

 

[Josi]

Small volume of course low-pressure or high-pressure tank.

An interesting concept for large volume long-term storage is hydrogenation. At least one company proposes this as a way to distribute hydrogen in fuel trucks, for a hydrogen economy.

Hydrogenation - Wikipedia

en.wikipedia.org

H20 Splitting by ionization

 

[Hedges]

Cracking water into hydrogen with battery power and then burning it in a (less than 100% efficient) internal combustion engine isn't likely boost vehicle range as much as, say, removing fan belt and powering electrical accessories from the battery.

 

[Wet1]

I never thought of drying food, that's an interesting idea!

Cooling, dehumidification, and heating DHW seem to be the most common energy dumps. Mining BTC can require faily significant initial capital expenditures, not to mention a learning curve to get there.

 

[Wet1]

I have my system pretty much at full use now. The addition of the two water heaters was what I needed.

I still don't understand why you didn't just preheat the DHW (using excess solar) inline before your main DHW heater. This would've been much easier, cheaper, cleaner, used less space in your living area, etc. Not to mention you have less heat loss through a larger single tank than you do through two smaller tanks (in your living area no less). But if nothing else, you did gain nearly instant hot water.

 

[copec]

I still don't understand why you didn't just preheat the DHW (using excess solar) inline before your main DHW heater. This would've been much easier, cheaper, cleaner, used less space in your living area, etc. Not to mention you have less heat loss through a larger single tank than you do through two smaller tanks (in your living area no less). But if nothing else, you did gain nearly instant hot water.

If they are anything like me, they probably scored used electric water heaters, and took whatever sizes they could get.

 

[sparrowhawk]

Unfortunaltely I cannot use a window air unit. My windows all slide open sideways. I do not have double hung windows. I did look for a mini-split, but that would only cool one room, and I already have central air. So even if I have a mini split, I would still have to run the central to cool the house anyway, there would be no savings. Thanks anyway!

Unless you have really narrow sliding windows I see no reason why you can't use a regular window a/c. I have used a few in slider windows by sliding the window against the a/c and filling in the open space above it with either plywood or plexiglass.

Also using a dehumidifier adds heat to the room. Why do that when you can get both cooling and dehumidifying by using a widow a/c.

The other thing you might want to consider is adding battery capacity to soak up excess solar so you can make it through the night while still using your window a/c or some other loads also at night.

I was in a similar situation as you where I didn't always make it through the night on my batteries and had lots of extra solar power during the day so I doubled my battery system and now I can go at least 3 days of cloudy weather.

I heat my water during the day, run a large sxs refrigerator, a 7cuft freezer, 6000 btu window a/c, my central a/c air handler fan, microwave, crock pot, TV, dvd, computers, and all my lights on a modest system.

 

[carefulmistake]

I’m going to use the inline water heater idea in my house build. I’ve got two 50 gallon heat pump units and I’ll run the first as a warmer and second as the main heater.

I may also look into using excess solar as a small indoor grow area for herbs with led grow lights and also schedule my erv to run more when there is excess energy.

 

[Repro]

Unless you have really narrow sliding windows I see no reason why you can't use a regular window a/c. I have used a few in slider windows by sliding the window against the a/c and filling in the open space above it with either plywood or plexiglass.

Also using a dehumidifier adds heat to the room. Why do that when you can get both cooling and dehumidifying by using a widow a/c.

The other thing you might want to consider is adding battery capacity to soak up excess solar so you can make it through the night while still using your window a/c or some other loads also at night.

I was in a similar situation as you where I didn't always make it through the night on my batteries and had lots of extra solar power during the day so I doubled my battery system and now I can go at least 3 days of cloudy weather.

I heat my water during the day, run a large sxs refrigerator, a 7cuft freezer, 6000 btu window a/c, my central a/c air handler fan, microwave, crock pot, TV, dvd, computers, and all my lights on a modest

Sorry for the delay. My sliding windows only have 18 inches on one side. To get more room I would have to completely remove the windows and build an insert that is insulated and weatherproof. I have two large windows in our living and dining rooms that have crank out windows. They will not accommodate any AC.

I keep a very close eye on my solar, and since the installation of the two 6 gallon 120V water heaters, my solar is literally maxed out now. That is exactly what I wanted to do. My gas bill has dropped less than $10/month, and it is a minimal savings. We actually turned off the gas water heater for a month to see how it affected our savings. We were disappointed in the low savings, but a savings none the less. Needless to say, we went back to our gas water heater again. The 6 gallon water heaters are still providing great hot water and maxing out our system while using less natural gas.

 

[sparrowhawk]

Sorry for the delay. My sliding windows only have 18 inches on one side. To get more room I would have to completely remove the windows and build an insert that is insulated and weatherproof. I have two large windows in our living and dining rooms that have crank out windows. They will not accommodate any AC.

I keep a very close eye on my solar, and since the installation of the two 6 gallon 120V water heaters, my solar is literally maxed out now. That is exactly what I wanted to do. My gas bill has dropped less than $10/month, and it is a minimal savings. We actually turned off the gas water heater for a month to see how it affected our savings. We were disappointed in the low savings, but a savings none the less. Needless to say, we went back to our gas water heater again. The 6 gallon water heaters are still providing great hot water and maxing out our system while using less natural gas.


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There are casement A/Cs that would fit your 18" windows. But I don't know how energy efficient they are.