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Reducing power consumption and energy wastage


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28 minutes ago, Paul Greeff said:

I have an API key from solarman for my plant but time has been a bit elusive the last few weeks. The plan is to use the additional information from the inverter, such as state of charge and production to determine when I switch on and the geyser. The pool pump will also be scheduled according to how much power is available on the day.

What information is available from your inverter? (a list of them provided by the manufacturer would be appreciated!) And how do you read this data (wiring, plugs etc.)

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On 2021/02/09 at 11:38 AM, Paul Greeff said:

I would appreciate some ideas to solve this problem without diminishing their enjoyment and convenience of hot water. I also looked at solar geyser, but I know too little about this at the moment, and I am concerned it will just shift the power problem to the winter when sun is not sufficient to heat the geyser

I don't think there is a way around this. You can't save money on hot water without changing your habits. 

 

In my previous home we had a solar geyser and to maximise the benefits you had to use hot water from midday until early evening. If you want hot water any time of day then you have to be heating water all day. 

 

There may be a small gain in using a timer to turn it off from, say, 11pm to 5am. Also by turning the temperature down. We don't use the cold water tap in our shower, and if we did it would suggest that we'd overheated the water. 

Edited by Bobster
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We've had the geyser on the timer now for a few weeks. I also added a thermal blanket to assist in reducing losses at night.

 

I am sure the situation will change a little bit in winter. As it is now, the geyser kicks in at 08h30 and shuts down again at 10h00. This is to allow other loads, washing, drier, etc, to get priority. At 12h00 the geyser kicks in again and is disconnected again at 15h30. The geyser was also turned down to 60C. It has dropped consumption to about 5 kWh per day from between roughly 7 and 10 kWh per day. That was a side benefit, the main problem addressed here was the geyser wasting battery at night, and this was successfully addressed.

One person has a bath at around 08h00 in the evening. The water is apparently still warm enough for a shower the next morning so its all good. We'll see what happens in winter.

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  • 2 weeks later...

Hi Paul Greeff, intelligently moving power from night time use to daytime when my panels are powered up is my pet project at the moment!  

I recently installed a 8KW Sunsynk inverter with 24 x 455W panels, 2 x 6kw/hr Bull Batteries. 

The batteries usually last me until about 22:00 after which I run on Eskom power until the sun comes up and I switch back to solar. 

My batteries are usually fully charged by 11:00 and I have surplus power after that.

I have an Intel Nuc which is connected to my Sunsynk via RS485 interface and collects live data regarding battery SOC, Inverter load and power from PV Panels, etc

The NUC is running Home Assistant, Sonoff LAN, Node Red, Influx DB & Grafana.

I have Sonoff switches on my lower power items and 63A eWelink Smart Breakers on my geysers, borehole, water heater etc

I am currently trying to work out how to set up Flows in Node Red to manage my loads and switch on heavy load devices on when the PV power production allows.

I was thinking of purchasing a 1000ltr wall water tank that I can heat up during the day with excess energy to provide radiant heat in my house at night.

  

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On 2021/04/07 at 11:06 AM, Sc00bs said:

I recently installed a 8KW Sunsynk inverter with 24 x 455W panels, 2 x 6kw/hr Bull Batteries. 

The batteries usually last me until about 22:00 after which I run on Eskom power until the sun comes up and I switch back to solar. 

I thought I was a heavy user. What's your load during this time that your batteries are drained by 22:00? Till what SOC do you run your batteries to? 

Your 12kwh batteries last you only about 4 hours from sunset to 22:00. I have 2kwh more battery capacity at 14kwh and they last me till 4:00 in the morning running them down to 25% SOC. 

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Have got staff cooking and a cottage also cooking, also have an on demand water heater that pulls 4kw when they are washing after work, have been thinking of switching that to a geyser that can heat up during the day rather.  SOC goes down to 20% so basically have 10kw/hr of power to use. Buying usually 10-15kw/hr a night so main goal at the moment is to reduce my continuous use items down as my base load is around 1.2kw

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I also have a cottage I'm renting out thats running from my inverter. First thing I did before getting the tenants was to put in a gas stove and oven. They have a 30l under counter geyser for their shower and kitchen which seems to work fine instead of the on demand hot water systems. My daily usage including my tenants is 35kwh per day. I also installed a private prepaid meter for them so they are now much more aware of their electricity usage. 

Cooking on gas works out better as you don't need to wait for a plate to get hot. Pots and pans are hot enough to cook fairly quickly instead of waiting for an electric stove to heat up so you also end up wasting less time and heat when cooking with gas. 

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1) I don't see the reason to switch anything to gas unless that is your absolute favored way of cooking or you want to have redundancy solution in case your PV trips out. Heating anything, but especially water with gas is more expensive than solar or solar PV will ever be + it's polluting + potentially a fire/explosion hazard + you have to replace cylinders when they run out + gas will go up in price over life of your PV system. Rather get a little more PV and storage and some energy efficient appliances.

2) Parasitic loads can make up a large portion of our night time loads eating away at the battery capacity. Switch off and unplug everything that is not absolutely essential and you'll be astounded how much you can save. Even 300W over 10 hours x 30 days adds up to 90kWh over a month. I have wired TV, amplifier etc etc so that I can switch it off on the wall when we go to bed - just get rid of all those little red standby lights and you will save 100-300W easy.

3) Water heating - get a bigger tank and low-flo shower heads and use your PV to heat it up. Some days there won't be enough sun, that's when Eskom will have to step in.

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20 hours ago, PeterP said:

1) I don't see the reason to switch anything to gas unless that is your absolute favored way of cooking or you want to have redundancy solution in case your PV trips out. Heating anything, but especially water with gas is more expensive than solar or solar PV will ever be + it's polluting + potentially a fire/explosion hazard + you have to replace cylinders when they run out + gas will go up in price over life of your PV system. Rather get a little more PV and storage and some energy efficient appliances.

Agreed with water heating via solar bring the best option. As far as the cost of water heating of gas vs grid my understanding is they cost the same.

But gas cooking has lots going for it. Battery storage for cooking can't compete presently. 

Edited by Richard Mackay
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DIY Geyser RetroFit system to be super efficient and cheap, killing 2 birds with one stone, 10kW storage the (amount of energy INSIDE a 200L geyser hot water and can "discharge 100% without any fears of damage - thanx to a member gave much appreciated calculation - batteries are not the only means of storage!) + 10kW generation, all in a simple 200L Geyser - a solution, add more geysers!?

 

I am going big with Solar water - 1000L currently - and adding another 800L - (we use LOTS hot water in the Birthing Centre with all the water deliveries) - my rule of thumb calc - will effectively mean 90kW storage (and 90 kW/pd Generation) - shudder to think what the cost in batteries would be!

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Speaking of water as an energy storage medium, I was thinking of using a 1000ltr water tank to store heat energy in during the day to heat my house up at night.

My PV Panels are capable of generating a lot more power as my batteries are fully charged by 12:00, was thinking of what I could use the extra power for. 

1000ltr Flow bin can hold water up to 60c safely, can then circulate that through a water radiator in my house to heat it up (wishing now I have put in underfloor water pipes when I renovated) 

Alternatively was looking at a Thintank for water storage as a big heatsink in my house, the aren't too confident on it's ability to store water over 50c though. 

Just heating the water up using a submersible element during the day.

http://thintanks.co.za/

 

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On 2021/04/10 at 8:52 PM, PeterP said:

2) Parasitic loads can make up a large portion of our night time loads eating away at the battery capacity. Switch off and unplug everything that is not absolutely essential and you'll be astounded how much you can save. Even 300W over 10 hours x 30 days adds up to 90kWh over a month. I have wired TV, amplifier etc etc so that I can switch it off on the wall when we go to bed - just get rid of all those little red standby lights and you will save 100-300W easy.

This is actually an interesting point.

I recently started buying up BNETA plugs to add power metering on as many places as possible in my house. Have 2 so far, waiting of another 4 to ship, and might need another 2-3 depending.

For now, the Sonoff POW R2 is on the Fridge, but more interesting, look at my office-feed for my own pc. Will get one for wife's office side later.

342069214_ScreenShot2021-04-16at9_12_30AM.png.84b062f3aac1b70f69260ef95e1e81fa.png

Above you can see it average at 60-70W with 2 Dell LED monitors, a 2015 MBP 13" a 5port gigabit switch and a polycom voip phone.
If I turn off 1 monitor, it goes to average of 50-60W.
If I turn off both monitors, it goes down to 20-30W.
If the laptop is unplugged from the charger as well, then it will be around 10-12W for the switch + voip phone.

In the past, I at times, forget to turn of the monitors and they run a screensaver the whole night.
So now, as soon as my alarm system is armed, the plug turns all of this off, which is a 20-70W saving as you can see in the above graph, around 9:30PM to 7:00AM.

 

This is the fridge graph. I am really impressed, most of the time it only runs at 88-91W usage. There is a part where it ran at 300W which I think is part of the cycle, because I only plugged this in yesterday. It does have a very short spike to about 570W.

1877472395_ScreenShot2021-04-16at9_18_00AM.png.b0d7e040ee1b9281b768349406d0d7f0.png

 

This is the main bedroom aircon. Currently it is cool enough at night to only use it in fan mode, which saves a lot of power. It is only on the really super duper host nights in Dec/Jan/Feb we need it in cooling mode.

2094734231_ScreenShot2021-04-16at9_18_10AM.png.2be2f4708b171e0d1dfed707d1b37d56.png

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