diy solar

diy solar

Excess Sun Power

Mini Tank water heaters that use 120V from an outlet.

That's an interesting little unit. But I don't know that it will do enough for you. 2.5 gallons will come up to temp pretty quickly and only takes about 0.5kwh. On a good solar production day, your excess power is 8kwh. Is this little heater enough of a diversion load to be worth the trouble?
A larger, pre-heat water tank is basically a bigger battery that gives you more value. IF you have space for it.

Electric car might be something to consider. You could pick up an older Leaf or Volt. They depreciated like a rock due to people's fear of the batteries. Depending on your driving pattern, you could eliminate some or all of your gas consumption. Then if the car fails, you have a battery pack to add to your system or sell :) My 2011 Volt (RIP) is now powering my house. There is a lot of insurance overhead with an "extra" car, but check out the Allstate Milewise service. You only pay for miles that you drive, so an extra car doesn't cost that much when not in use.
 
I am using a 40Amp Magnacraft 12V DPDT relay.


Text says DPDT, photo shows DPST (which wouldn't provide transfer switching)

It is very much like the Dayton one I used. (was switching heating elements series/parallel, and thing it created a bonded fault.)
I suggest at least having a fast fuse to hopefully protect your inverter, and hope it never connects in such a way as to fight with the grid.

I'm using a UL listed Square-D interlock as a manual transfer switch. I wanted to be certain my expensive inverters never backfed the grid out of phase.
 
I used an ECOsmart6 in my system for years and they have low heat loss. You might as well get a 6 gallon to keep the heat overnight. It takes less than 900WH to bring that much water up 60F. One bad thing is it won't go above 125F even though it says on the box. Legal made them turn it down. I had another 9 gallon in series as a preheat till that started leaking. Just to see how well it would work I bought a 150L (13gal) that was only $150 shipped. I run this off solar and heat loss was horrible compared to the ECOsmart. Had to box it in with extra insulation to keep it from dropping to ambient overnight. Square is ECOsmart and horizontal is 150L.
CampHW9-16-21HD.jpg
My garage has a 40 gallon and the top 15 gallons heats easily. Any excess pre heats the bottom. Stratification is a great way to do it with solar. This tank is just for laundry and I can get two loads using hot water for all cycles with just 1-2KWH a day diversion. Both tanks only heat by diversion. I don't think most realize how much power they throw away each day.
 
I used an ECOsmart6 in my system for years and they have low heat loss. You might as well get a 6 gallon to keep the heat overnight. It takes less than 900WH to bring that much water up 60F. One bad thing is it won't go above 125F even though it says on the box. Legal made them turn it down. I had another 9 gallon in series as a preheat till that started leaking. Just to see how well it would work I bought a 150L (13gal) that was only $150 shipped. I run this off solar and heat loss was horrible compared to the ECOsmart. Had to box it in with extra insulation to keep it from dropping to ambient overnight. Square is ECOsmart and horizontal is 150L.
View attachment 92714
My garage has a 40 gallon and the top 15 gallons heats easily. Any excess pre heats the bottom. Stratification is a great way to do it with solar. This tank is just for laundry and I can get two loads using hot water for all cycles with just 1-2KWH a day diversion. Both tanks only heat by diversion. I don't think most realize how much power they throw away each day.
This is very interesting. I am adding it to my research list. Thanks a lot and keep the ideas coming.
 
I'm planning to do the same - use excessive energy to heat water. But since I'll do this through a heat pump it is not going to use all the energy.

One option that crossed my mind is to store the excess energy as hydrogen. But this was just a spike and I haven't researched many details. Some statements said that the conversion efficiency is ~80%. And we do aim for a clean future there is some chance that this will become mainstream.
 
Heat pump water heaters unfortunately can't absorb that much excess power, about 500W. Adding that excess power using the existing heating element is a good idea. HPWH become less efficient the higher the temperature goes. Excess to resistive can raise the temps much higher for overnight loss. In winter, PG&E did an engineering study that said the actual COP dropped 44% based on natural gas heating. Resistance heating doesn't seem so bad considering that.
 
One option that crossed my mind is to store the excess energy as hydrogen. But this was just a spike and I haven't researched many details. Some statements said that the conversion efficiency is ~80%. And we do aim for a clean future there is some chance that this will become mainstream.

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.

 
Great news! I added two 6 gallon water heaters (ecosmart 120V) and they work great. Bad news, once they heat up the water to temp, they hardly use any power. So I still had excess power. Now that the days are even longer, I tested out our dehumidifier for an extended period of time and it works great. I have the dehumidifier on 24/7 for the past 8 days straight and I am now getting what I think is the best potential from my big system.

My smaller system makes 1400W/h in full sun and once the batteries are full, I had unused power there as well. One of my neighbors has an e-bike and an e-scooter, and now charges them during the day with my small system in my garage. We run the power through a Kill-A-Watt and will pay me for it. We tested it out, and it works perfectly. We haven't worked out how much he will pay yet, but once we get a handle on the amount he uses, we will work something out.

Thank you everyone for your input. I love the fact that we are getting the most out of our system now.
 
Yup, they don't take much to heat up. Less than a KW. This is the daily temperature cycle of my ECOsmart6.
ECOsmart_2day.png
 
Yup, they don't take much to heat up. Less than a KW. This is the daily temperature cycle of my ECOsmart6.
View attachment 94166
These ecosmart's are great. Instant hot water, and REALLY hot. I installed a bypass valve so that I can switch to either the ecosmart's or the main hot water line. One of the ecosmart's was installed in the secondary bathroom, I bought a hose with shower head and attached it to the sink. The shower head has a on/off valve. I then showered with the 6 gallon's, and it lasted the whole shower. We have an RV that also has only a 6 gallon tank. If you shower like in the RV, it works with no problem. I am thinking of a way to run a line to my shower from the ecosmart with a bypass valve as well. That would be a big energy saver. It also forces you to save on water as well. So fast daytime showers will be heated by sun power.

I love this solar stuff!
 
We have a geothermal heat pump and a preheat hot water heater/tank. The elements of that preheat tank are not connected at all. We get waste heat in the summer and heat pump heat during the winter to preheat that tank. I have been thinking about dumping some of my solar emergency system's PV to that tank. We are grid tied with a main system and a separate secondary array just for emergency power. I have been doing some experiments with using it for resistance heating in the garage during the winter....just messing around with it.
think of the solar as a "pre heater"- it pre heats the water before it goes into the main tank.
 
I do want to warn anyone interested in the ecosmart 6 gallon water heaters. They are big and need lots of space, so if you are looking to install one, get the dimensions and measure. I had to heavily modify a big dual sink vanity to shoe horn it in. Now there is little to no useable storage space in the vanity. The other one is installed on the wall in our utility room and ran the plumbing along and behind the wall to the sink. I just installed two "T" fittings and ran hot water to the utility sink and wash machine as well as a back up. The wash machine really makes the solar work hard. We are getting lots of use from them now and this was definitely worth it.
 
Big, but it pays to have the extra insulation. I think that is how I got mine. Bought off craigslist for $75 because the guy never got around to installing it. Probably wouldn't fit under his sink.
 
When I have excess solar, I lower the temp on the air conditioning.

I have a 57 kWh battery and a Chevy Bolt EUV with a 66 kWh battery.
Excess solar happens when both show they are "fully charged".

This actually rarely happens though. My usage is usually around 600W for the house. I easily use 9kW doing the laundry when the air conditioner turns on. I have an 11 kW EVSE for my car, but seldom use it higher than 4 kW.

Another option for "excess solar" is to feed it into the grid. Don't expect any kind of financial gain anymore doing this. The "balance" with my utility is -7.81. This is barely covering the minimum service connection fees.
 
When I have excess solar, I lower the temp on the air conditioning.

I have a 57 kWh battery and a Chevy Bolt EUV with a 66 kWh battery.
Excess solar happens when both show they are "fully charged".

This actually rarely happens though. My usage is usually around 600W for the house. I easily use 9kW doing the laundry when the air conditioner turns on. I have an 11 kW EVSE for my car, but seldom use it higher than 4 kW.

Another option for "excess solar" is to feed it into the grid. Don't expect any kind of financial gain anymore doing this. The "balance" with my utility is -7.81. This is barely covering the minimum service connection fees.
Net metering varies from localities. I'm grandfathered for at least 10 years for a 1:1 swap.
 
When I have excess solar, I lower the temp on the air conditioning.

I have a 57 kWh battery and a Chevy Bolt EUV with a 66 kWh battery.
Excess solar happens when both show they are "fully charged".

This actually rarely happens though. My usage is usually around 600W for the house. I easily use 9kW doing the laundry when the air conditioner turns on. I have an 11 kW EVSE for my car, but seldom use it higher than 4 kW.

Another option for "excess solar" is to feed it into the grid. Don't expect any kind of financial gain anymore doing this. The "balance" with my utility is -7.81. This is barely covering the minimum service connection fees.
Net Metering or Net Feedback is a can of worms I do not want to get in to. The additional costs, inspections and bureaucracy involved are not worth it. I would rather find creative ways to use the energy I am generating. The addition of the two 6 gallon water heaters were the perfect solution to maximizing the use of my daily power excess.

The really cool thing is that in winter when the days shorten, I can bypass the water heaters and save the power for more critical loads. Unfortunately I do not have 240V split phase inverters, battery and panel capacity to run my AC, that would be awesome. Thanks for your input!
 
You could get a window air conditioner or mini-split sized to the power your PV does generate.
 
You could get a window air conditioner or mini-split sized to the power your PV does generate.
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!
 
Back
Top