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How can I make the best use of my surplus solar power that the grid can't accept?

Image credit: Sunday Solar

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Dragan Otasevic
Dragan Otasevic Dec 17, 2021
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How do I make the best use of an excess 10-19 kW of electricity during sunny days? In practice, this means between 10.000 - 19.000 Watts of "free" household electricity from 9 am to 4 pm.
Details
I have an unfortunate problem. I built a 37 kW solar power plant. It's grid-connected, but the grid can only accept 14.4 kW. In the winter months when the sun is low, this is fine. The entire array rarely peaks over 14 kW. But in the summer months when the sun is high, the plant will always make excess electricity. The grid cannot take it and I currently don't have a way to spend it locally.
The power grid wants me to pay for the local grid upgrade if I want to send them higher throughput. They communicate with me only in written form and reply once every 6 months. At this pace, it will take a year before I even get a cost estimate and then more time before any progress is made. The kicker is, the grid will resell my energy to other people but won't pay me for it. I get credit for it, but I have to use it for electricity consumption by the end of the year, or they consider it a gift and reset the counter at the end of each year. Their rationale being "private solar power plants are meant for self-consumption, not profit".
So for the excess power, it's a "use it or lose it" type of situation. How can I use it to recover the cost of equipment, or god forbid, make some money?
Any good solution should take into consideration that the excess is:
  • only half of the year (from mid April to mid October)
  • only during sunny days
  • only during peak hours (9am - 4 pm)
  • is unpredictable during partly-cloudy weather
  • can only be used within the household
15
Creative contributions

Collaborate with Neighbors and Channel it into EV Charging

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Oguntola Tobi
Oguntola Tobi Dec 17, 2021
If you have people who use electric vehicles in your neighbourhood, collaborate with them, build an EV charging station and have them charge their vehicles for a fee, if the money is worth it.
Alternatively, you can purchase an EV yourself and use the excess power for charging it.
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J. Nikola
J. Nikola9 months ago
This was my idea too. Since rural areas and villages often do not have EV charging stations, you could create a private pop-up charging station for people passing by. You could also make it profitable by placing a stand with local food or putting it next to a local restaurant.
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Oguntola Tobi
Oguntola Tobi9 months ago
Lol. You've ideated a business conglomerate for Dragan Otasevic.
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J. Nikola
J. Nikola9 months ago
Oguntola Tobi It's not about finding opportunities but creating them. :)
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Cryptocurrency mining

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Dragan Otasevic
Dragan Otasevic Dec 17, 2021
I was going to do bitcoin mining, but I see that the cost of modern mining rigs has grown to above 15K EUR apiece.
So a GPU mining rig would be the way to go. The rig could be used to mine whatever crypto is worth mining at the moment and continuously sell/convert it to bitcoin.
I would run the rig on only during excess solar power and turn it off when the production drops below 14 kW.
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Neighbours?

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Povilas S
Povilas S Dec 17, 2021
Do you have any close enough neighbours to sell the electricity to, give it for free or exchange for some goods they can offer you? An eco-community can be built this way
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Shubhankar Kulkarni
Shubhankar Kulkarni6 months ago
I think this is the optimum solution since the excess power generated is not dependable (since it is mentioned in the challenge description that you will get it only half of the year (from mid-April to mid-October, on sunny days, and in peak hours). Use it as an inverter. Whenever there is excess energy, it enters the main power supply of the neighborhood. That temporarily stops the power supply from the regular source. Once you are exhausted, or when the weather is cloudy, or after sundown, the main power supply switches back up. There is no hindrance during the transfer since it's just a few houses and the backup power (a main power supply source) is right there. You just need one connection from your solar grid to the power supply line that supplies power down the street. You may attach a meter there to see how much power you provide to the households. If you want, you could charge them for the power at a lower cost, since it is green energy and you don't incur much cost to generate it.
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Povilas S
Povilas S5 months ago
Shubhankar Kulkarni The excess won't be enough to replace the main power supply for the neighborhood (unless it's a single house with little energy needs). If you replace their main supply with the excess power from Dragan's solar panels, even for a short time, each of them will only receive a very weak current, this would be a waste of the excess power.
That's why I talked in the comments about neighbors using batteries to store the excess power transmitted from Dragan's house through wires.
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Dragan Otasevic
Dragan Otasevic9 months ago
I do have neighbors but there's no simple solution to set things up. I would need to complement their grid-connected system only during excess production, but not during the night, morning, and evening. Neither during the winter nor cloudy days.
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Pump water uphill during excess, run turbines with it at night

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Darko Savic
Darko Savic Dec 18, 2021
I'm not sure how feasible this is in your case. It would require quite a few large cisterns or a large pond to be built on top and below a nearby hill.
When you have excess power, use it to pump the water from under the hill to the top. Then at night, drop the water through turbines. The water returns to the bottom holding area and in the process generates electricity. You can control the throughput to not go over your limit (14 kW).
It might be cheaper to just pay for the grid upgrade though.
With the right kind of pump, the same equipment could be used to move the water uphill and generate electricity downhill (pump running in reverse).
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Shubhankar Kulkarni
Shubhankar Kulkarni12 days ago
Here is a way to pump water uphill to an extent without using electricity. The video was sent to me and I could not locate the source.
The person built the device using PVC pipes. He pushed and retracted the downward arm (the left-most part of the device) 4-5 times in the river. There were a few initial bursts of water and once the water filled the entire device, he did not need to keep pushing. He then placed the device on the ground and it could pump water out of the river through the end on the right in a continuous flow.
For the current idea, we will need a bigger device. Here, the person could manually push the device into the water. When the device is bigger, we might need electricity to initiate the water flow. Once the flow is stabilized, electricity will not be needed.
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Irrigation

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J. Nikola
J. Nikola Dec 20, 2021
Since the surplus happens mostly during the summer, when the temperatures are high, you could use it for irrigation. You could use the electricity surplus to pump the water into the reservoir located uphill or on the platform that is higher than the field. Then, during the night, you could open the valve and use gravity to water your plants. Since you have a lot of electricity at that time, you could create a huge container or an artificial lake, pump the water all summer and use it for large crop fields or orchards!
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Darko Savic
Darko Savic5 months ago
This is a cool idea. The amount of water would be enormous if 10-14 kW of excess power was used for this on good days.
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Invest in Power Backup + Cold Storage with room to play for monetization

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Aashi Agarwal
Aashi Agarwal Mar 24, 2022
A cold storage for summer months would make great sense when you're starting off without really committing to a specific idea because it leaves room to play around with a wide variety of low risk monetization options while still being useful to you personally.
A lot of products require cold storage, you could benefit by leveraging the niches in your local community, perhaps a particular fruit would be loved by all if available just after summer, as wedge to enter an immediate market with your neighbors.
It's low risk, has material returns plus scope for monetization, and the assets purchased to use up the extra energy will last for last years so it depreciates slowly.
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Dragan Otasevic
Dragan Otasevic5 months ago
Even a very efficiently insulated cold room would need to run 24 hours per day. To burn 10-14 kW excess it could be really huge. In the nighttime, this could amount to quite a cost.
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Indoor farming

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mschiav3
mschiav3 Apr 11, 2022
You can build a vertical indoor farming tower/building for some high-value vegetables. Depending where you live, you can use the extra energy to provide a defined light during day time and heating for your farm, and sell your produce even during winter for crops that are of summer time. Using a very enclosed system also allows you to produce it almost organically. I would recomend tomatoes or cucumbers, if you want to try some hard to do indoor farming, however, leafy-greens would be easier to produce.
Being very farfetched on that idea, producing indoor strawberrys or even grapevines and establishing a small winery would be very cool also.
Wallmart has been investing in that sector in california, might be the start of a startup. Food security is one of the biggest challenges of our times ;)
References:
https://www.youtube.com/watch?v=QT4TWbPLrN8
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Dragan Otasevic
Dragan Otasevic5 months ago
I would go for something like indoor vanilla and market it as the (only?) brand produced in my country
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Darko Savic
Darko Savic5 months ago
You can (over)size the farm just enough to use the excess electricity on good days. On bad days you pay for the use, but you would have recovered the investment when you sell the produce.
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Crypto Mining

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Seshu Kumar
Seshu Kumar Apr 10, 2022
Crypto Mining could be your alternative. Since its just a machine that you can control by turing on only when power is excess and turn off during the rest of the time , you can have everyting under your control.
But it does require significant amount of investment initially to by the GPU mining rig.
you can use this link to check your which GPU's could give you best value. https://whattomine.com/
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Dragan Otasevic
Dragan Otasevic5 months ago
I did that about 10 years ago. I invested a lot of money into rigs. The GPUs burn out after a while, the rigs are noisy and can't be kept in the same house where people live. I was going to do liquid cooling and run that into my home's central heating but eventually gave up on the idea because too many GPUs burned out.
The only way I was able to recover my investment is because the value of the mined crypto increased and I didn't sell it. All in all, not something I would recommend to others. I would have made a lot more money had I just bought crypto instead of the mining rigs.
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Produce Hydrogen by using the extra current to split water molecules

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mschiav3
mschiav3 Apr 11, 2022
You can establish a current using two electrodes in salty water and produce molecular hydrogen. You can burn it for fuel when there is not that much sun around. You can use it to power a stove or a heater. You can use it to power a hydrogen cell car. You can make balloons with it (might be dangerous). You can also sell the hydrogen produced or the oxygen produced (it would have been helpful during the hardest times of the pandemic).
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Dragan Otasevic
Dragan Otasevic5 months ago
Not bad. This guy explains it well:

It looks like for the time being, lithium-ion batteries are cheaper and almost twice as efficient as the safe home hydrogen solution proposed in the video.
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Start a glassblowing business

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Devin Holland
Devin Holland Apr 14, 2022
An electric furnace would consume about 10KW and cost somewhere around $20k. Hire a teacher and provide lessons. The lessons I've seen are $100-$300 for a single person each visit.
https://www.cannedheatglass.com/product-page/80-electric-moly-mosi2-furnace-1-phase
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Dragan Otasevic
Dragan Otasevic5 months ago
This is a pretty cool, unique solution. It would be viable for someone who is into glassblowing and has enough customers/work to run the furnace every day.
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Use excess energy to heat water

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Michaela D
Michaela D Apr 25, 2022
Solar energy is used widely to heat water, usually in combination with traditional heating. On warm, sunny days you can rely solely on your solar panel and during the winter you use your traditional water heating system. There are different types of solar water heating categorized into two main groups: active and passive. Depending on your solar and water heater system setup and the climate one group may be better than the other.
According to this article your water heater needs 1,5kW/hour. With your surplus of 10-19kW you would have enough power to heat your water for the whole day. Based on my experience with a thermosiphon system the water stays warm at least for 4-5 hours after the sun is gone.
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Michaela D
Michaela D5 months ago
This seems like an obvious solution. Is there a reason you are not already doing it?
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Dragan Otasevic
Dragan Otasevic5 months ago
Michaela D I actually am doing it. Heating a pool with the excess.
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Michaela D
Michaela D5 months ago
Dragan Otasevic makes sense! Could you not use it to heat water for the whole house?
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Freeze dry seasonal fruit and sell it offseason

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Darko Savic
Darko Savic Dec 21, 2021
Freeze dryers use a lot of electricity. They completely dehydrate food and make it last for years without the need for refrigeration.

When you add water, freeze dried food returns to almost as it was before. You can also eat it dried. It's crispy and has the original flavor.
You could freeze dry seasonal fruit and sell it off-season or find a ceral manufacturer that would buy it from you.
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Charge a battery bank only with excess electricity

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Darko Savic
Darko Savic Dec 28, 2021
Configure the equipment so that a battery bank gets charged with any power that is in excess of the maximum (14 kW) that the municipal grid can accept.
If you properly size the battery bank you will have used the stored power at night (air conditioning, household refrigerators, etc).
If you don't use that much power at night, you could figure out a way to empty the battery bank by pushing electricity into the municipal grid during the night. That way you start empty every morning.
But since the municipal power grid doesn't pay you for the credit that you build up, you will need to use it up during the wintertime.
Come wintertime, in addition to heating your home with electricity, you could also heat a swimming pool or a greenhouse.
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Semi-private power grids

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Contrived _voice
Contrived _voice Mar 24, 2022
I had this idea that solves this problem. By connecting everyone in an area that used solar panels, You could merge the excess power output from each household and share it with the households that didn't have solar energy.
When these houses paid their power bills at the end of the month, Some of the money would go to the private electricity poviders proportional to the power consumed. Since this energy is cheaply produced, you could charge lower rates allowing people to use green energy solutions while saving money.
All it would require is a "control station" to regulate the power input from the main grid whenever output from the solar station dipped below the power consumed by the houses in this mini-grid.
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Compressed air in a large underground steel tank encased in concrete

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Darko Savic
Darko Savic May 02, 2022
Here's an idea I haven't researched at all for feasibility. I'm just putting it out as a placeholder:)
A large underground tank made out of steel encased in concrete and buried. During peak power, you use a pump to fill the tank with air to extremely high pressure. During the night you gradually let the air out via the same pump that now runs in reverse and creates electricity in the process.

You push the night-time electricity into the grid to your 14 kW capacity.
You should be able to calculate all the details such as:
  • how much peak electricity you have available on a good day
  • how much air a compressor can move with that kind of power
  • how big of a compressor you need
  • how big of a tank you need and how much force it needs to endure
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General comments

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Spook Louw
Spook Louw9 months ago
This is not my area of expertise at all, but I wonder, would you be able to turn the excess energy into elastic energy by using it to wind up a coil or recoil a spring? I'm sure a lot of the energy would be lost (and the spring would have to be quite large, perhaps unpractically so). But winding up a coil would allow you to store it as elastic potential energy to be released when you choose.
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Darko Savic
Darko Savic9 months ago
Spook Louw that would require a lot of purposefully built equipment. Safety would be tricky as well. Along these lines, kinetic energy could be stored in huge flywheels:

The flywheels would be slowed down in the evening and throughout the night by running dynamos.
Check out the flywheel bus:
And flywheel battery:

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Spook Louw
Spook Louw9 months ago
Darko Savic Sounds like a business opportunity. Surely there are other people with similar problems.
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