Excess energy in off grid system

[GSXR1000]

victron charge control can switch an output once batteries hit a certain voltage.

I am working on this turning on my absorption fridge

 

[newbostonconst]

What's a normal tank? And what temperature differential?

From a cold start (e.g. 10C) a 320 litre tank requires about 20kWh to raise water temp to spec (60C).


In Australia we have several solar PV diverters for hot water systems:

Hot Water PV Diverter Comparison Table

View a list of all the solar hot water diverters on the Australian market we know of, plus pricing information and technical specifications.

www.solarquotes.com.au

I'd imagine similar would be available where you are.

Delta temp for a hot water tank is more like under 30 degrees C. Your results are around doubled, so more like 10kwh for the size tank you referenced. That is if you have a tank filled once a day with cold ground water and thus an extra tank.

For most tanks that are keep warm for use the heat variation daily would max from 40C(104F) to 60C(140F), so 7kwh which is around what I stated and that is if you could sync your showers with when the sun is out.

Another way to look at it is , a five min shower uses 6 gallons or 24 liters of water. So heating from 10C(50F) to 60C(140F) would use 1.4kwh.

Either way you look at it adding a tank to store hot water, it is cheaper now to buy batteries and use the power as needed and not worry about a tank cooling down.

"Calculate the kilowatt-hours (kWh) required to heat the water using the following formula: Pt = (4.2 × L × T ) ÷ 3600. Pt is the power used to heat the water, in kWh. L is the number of liters of water that is being heated and T is the difference in temperature from what you started with, listed in degrees Celsius."

 

[wattmatters]

Delta temp for a hot water tank is more like under 30 degrees C.

You were talking about the amount of energy stored in a tank of hot water, not the daily energy required to keep it hot. These are quite different things.

Our daily average for our hot water is 5kWh/day. It has one heat cycle/day (overnight).

How much energy any household needs to use for their daily HW obviously depends on the temperature of the water entering the tank, the temperature setting of the tank, the amount of hot water the household uses and where the tank is located, ambient air temperature etc as there are heat losses through the day, and of course the type of hot water tank (e.g. resistive element vs heat pump). Our tank's daily heat losses are ~2.3kWh/day and it is located inside our laundry. Many HW tanks in Australia are located outside and can have experience greater heat losses. In northern US I'd expect most tanks to be inside a building to avoid freezing water in pipes.

 

[Ai4px]

I am planning to go off grid. I will had a tesla battery system. Do I have to do something with the excess energy if the batteries are full. Do I need some type of dummy load and how would I switch over to it.

I don’t think you’ll be off grid with a Tesla Powerwall. It has to phone home every three days. Does not sound off grid friendly. Homemade with lfp batts or generac May be better.

 

[chrisski]

I can’t speak to the TElsa power wall, but with solar and batteries, you don’t need a dummy load.

If you had wind, you would need a dummy load. For when I looked at wind, the dummy load was built in so this load was a component added on to the system to make it transparent to you. Years ago I saw some people who used a 500 or 1000 watt space heater As a dummy load, but the newer systems I looked at these dummy loads were components were built in to the windmill that you did not even notice them.

Hydro seems to need the same dummy loads, but not many people can use that. Nuclear power needs a dummy load also, but don’t know anyone using that as a home system.

 

[GSXR1000]

I can’t speak to the TElsa power wall, but with solar and batteries, you don’t need a dummy load.

If you had wind, you would need a dummy load. For when I looked at wind, the dummy load was built in so this load was a component added on to the system to make it transparent to you. Years ago I saw some people who used a 500 or 1000 watt space heater As a dummy load, but the newer systems I looked at these dummy loads were components were built in to the windmill that you did not even notice them.

Hydro seems to need the same dummy loads, but not many people can use that. Nuclear power needs a dummy load also, but don’t know anyone using that as a home system.

why would nuclear need dummy load... it is just steam and you can bypass the steam going to the turbine strait to the cooling tower

 

[chrisski]

why would nuclear need dummy load... it is just steam and you can bypass the steam going to the turbine strait to the cooling tower

Perhaps. I’m certainly no engineer. Nuclear power tends to provide really cheap electricity at night. Perhaps its to send the steam to the turbines instead of the air. My point to the post was solar doesn’t need dummy loads.

 

[labeeman]

why would nuclear need dummy load... it is just steam and you can bypass the steam going to the turbine strait to the cooling tower

I would not like to live near a nuclear plant that has to let off steam as it is radioactive at times.

 

[labeeman]

I can’t speak to the TElsa power wall, but with solar and batteries, you don’t need a dummy load.

If you had wind, you would need a dummy load. For when I looked at wind, the dummy load was built in so this load was a component added on to the system to make it transparent to you. Years ago I saw some people who used a 500 or 1000 watt space heater As a dummy load, but the newer systems I looked at these dummy loads were components were built in to the windmill that you did not even notice them.

Hydro seems to need the same dummy loads, but not many people can use that. Nuclear power needs a dummy load also, but don’t know anyone using that as a home system.

Hydro dummy load is to pump the water back to the reservoir.

 

[Roswell Bob]

extra solar...hehe... people always have very different setups and it certainly shapes they view point.
for example, I have a small place and consume about 50Kwh/day...so the first thing I thought reading the above was "Wow, that guy much have a huuuuggge solar panel farm to have extra power"

At 50kWh/day you must be growing weed or pouring anvils Please tell what you do with all that juice.

 

[GSXR1000]

I would not like to live near a nuclear plant that has to let off steam as it is radioactive at times.

it doesn't let steam into the air.. it redirectd it to the cooling tower, lake, ocean.. what ever method is being used

 

[upnorthandpersonal]

It is surprising how much extra power there is with a solar system. I heat all the house water with only excess PV, be it just a few watts or hundreds. It can be as short as just a few seconds, but it adds up over the day. Just random collection, hot water has lowest priority.

It's what I do as well. 10kW array with 5kWh/day electricity use at most, the rest goes in a 3000L water tank. Still offsets the wood requirements once it gets colder/darker outside, except of course for dead of winter when we don't see the sun at all.

 

[efficientPV]

it doesn't let steam into the air.. it redirectd it to the cooling tower, lake, ocean.. what ever method is being used

Those red and whit towers are for off gas, dispersal before it hits the ground. I climbed one in Japan, lucky I never got caught. It is a shame bean counters destroyed part of that country. There was no damage to reactor. They put backup generator too close to ocean. First thing wiped out was fuel tank. You don't know how many events have occurred which have gone unreported.

 

[Hedges]

I would not like to live near a nuclear plant that has to let off steam as it is radioactive at times.

it doesn't let steam into the air.. it redirectd it to the cooling tower, lake, ocean.. what ever method is being used

Normally, no radioactive water would be released. It is in a closed loop, with heat exchanger to the water used for turbine and cooling tower.
Leaks and loss of cooling, that's another story.

Still, tritium is the least of your worries. So long as it gets distributed widely and diluted it'll never be enough to affect you. It is all the other elements getting concentrated in the food chain and your body which are a problem.

 

[chrisski]

I truly regret my nuclear energy comment. It has entirely hikacked the OPs thread. I should have just stuck to the statement, “Unlike other energy methods, Solar does not require a dummy load.

 

[Webbee]

Is there a way to divert extra solar energy into another battery bank that can be used as backup storage for those cloudy days?
My system isn't that large but I use around 20-25% per day. This runs my freezer and basement lighting 24/7. I have 600 watts of solar, Victron 250/60 charge controller and a 2000 watt pure SW inverter. I was thinking if I had two more batteries on stand-by I could use them to recharge my main battery bank for those cloudy days. Does anyone do this? Or would it just be wiser to just added them into the system? I enjoy building and experimenting with different ideas. I am curious how people will respond!

 

[labeeman]

Is there a way to divert extra solar energy into another battery bank that can be used as backup storage for those cloudy days?
My system isn't that large but I use around 20-25% per day. This runs my freezer and basement lighting 24/7. I have 600 watts of solar, Victron 250/60 charge controller and a 2000 watt pure SW inverter. I was thinking if I had two more batteries on stand-by I could use them to recharge my main battery bank for those cloudy days. Does anyone do this? Or would it just be wiser to just added them into the system? I enjoy building and experimenting with different ideas. I am curious how people will respond!

It would be wiser to just add them into your system

 

[chrisski]

I’m sure it could be done, but I gave up on that.

As far as just adding the batteries on: depends…..Would not be the best idea to add batteries on this system if they are lead acid. Lithium is much easier to add batteries on.

For charging a different system you can look at things like battery isolators. The problem I did not want to tackle is the switching over portion. What happens when you drop two huge capacity batteries in a system? Would the inrush really be that much. You could isolate them with a high voltage DC switch, but how do the loads react to that monetary loss of power when its switched? For example air conditioning on and the battery bank switched Would cause the AC to go out and then spin back up.

THese issues were too much for me to work through.

When I decided to upgrade my 4 FLA golf cart batteries, I could not just add on 4 more, so I went with the equivalent in a lithium build. If I want to add to these lithium’s at a later date, I have phisical room to add 50% more battery power.

 

[wattmatters]

Or would it just be wiser to just added them into the system?

This

 

[pollenface]

With wind power you need to do something with extra energy. Solar you do not.

Not necessarily. I have been using voltage sensing brakes as oppose to dump loads and they work 100%. While the brake is on (28.7v in my case) the turbine only shows you which way the wind is blowing but doesn't actually spin.