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Reducing power consumption and energy wastage


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Our solar installation at home went live on Friday afternoon, so we've only been on solar for a few days.

I am blown away by how useful the logger on the Sunsynk is. We need some assistance in reducing the consumption.

To give some context, we're four people in the main house where we have the solar solution (soon to be five), and then two in the cottage where my folks live. We've identified some wasteful loads that we can address, but others are a bit tricky to address.

 

The main house consumption only deviates a little bit as we have a gas stove and geyser. During the day we try to introduce the heavy loads only when there is sufficient sun and battery capacity to handle the peaks. The cottage has an electric stove and geyser.

1. Stove / Oven - we're looking into a modern gas stove / oven (not the gas stove electric oven combo). We should have that installed in a few weeks once we've decided on a model so this isn't a major concern.

2. Then there is the geyser. I have a number of ideas I want to try, but for the most part, I don't know how to get rid of the thing. So far the best I've come up with is a thermal blanket as it's insulation is very poor. And then of course a timer to shift as much of the load to the day. I would have liked to install a gas water heater such as the one we have in the main house, but the old folks don't like 'personality' of the gas heaters and I don't want my solar hobby to become a point of contention.

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.

3. Small loads that add up to a lot of power. We still have to identify these little buggers. They're all over the place. For example, I have three fridges and a freezer, and then the fridge and freezer in the cottage, plus the fridge in the caravan. Just switching off the fridge in the caravan noticably dropped our usage over night but we're still hunting for other items to disable. We're between 450W and 850W the whole night (excepting the geyser of course) which still depletes the batteries way before morning. But we'll carry on hunting for these culprits.

 

So my main concern at the moment is how to reduce and shift the geyser consumption as much as possible. Thermal blanket and timer are a start, but do we consider a solar geyer or heat pump? Or even a modern electric gas water heater with electric control etc.? I would very much appreciate your perspective on this.

 

Regards

Paul

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Another sneaky one that could get you is lighting. If you don't already have LED lights everywhere, then switching to LED lights could reduce your nighttime consumption significantly. When we moved into our current home, the previous owners had put in 100W halogen lights all over for some reason. The first thing I did was replace them with LEDs.

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We've installed solar hwc instead of the original electric one, in winter, you can't expect to get a hot shower at 11PM, but mostly its works pretty well, it has only been running since July last year, so don't take my word as gospel on the matter, also where you are located is a factor, in the Orange River valley here, so, southern Kalahari and winter is 2 cloudy days, with one of those a bit of drizzle, else blue sky and sunshine, thus no blanket to keep the daytime warmth around after sunset...

The HWC is 10? can't remember, evacuated glass tubes going to a 100l? maybe 200l? storage tank, all is gravity fed, no municipal water, net kanaalwater of boorgatwater.

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I would have loved to do it that way, but unfortunately the cottage is not connected to the main house. 

 

However, we are considering a timer for now, I just need to figure out if the timing works.

Unfortunately the one likes to take a bath in the evenings after sunset, and the other prefers early mornings before there is any irradiation worth talking about. Not an ideal combination.

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Why not another solar install for the cottage? 

1.5kW element definitely.

I like the CBI Astute as a timer switch for my geysers, allows me to remotely manage it on an app, well actually mine is also connected to home assistant and wrote automations to schedule it 1hour a day and 5 hours on a sunday to keep the geyser clean from legionnaires. 

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I'll see about sourcing a smaller element. Does it make such a big difference? Perhaps to squash the peaks a bit?

The timer is definitely in the works, but ideally I would like to rid us of anything with large current draws outside of daylight hours. Would you mind sharing your schedule for the CBI on the geyser, and well as when you typically use the hot water?

 

But for now, timer, blanket and heating element for the geyser should help. They're all quick wins, but ultimately this problem is not solved properly yet.

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I have 2 geysers in the house, both get used at different times. Also don't have solar yet so that hasn't changed the way I schedule them. Mostly, they set to reduce power usage to save money.

Main bedroom geyser goes on around 4am for 60minutes monday to saturday. On sunday it goes on around 4am for 5 hours.
Usage for this geyser, is 2 showers from 5am in the morning.

Geyser in front of house, goes on around 3:30pm for 60minutes monday to saturday. On sunday it goes on around 4am for 5 hours.
Usage for this geyser, is baby getting a bath around 5-6pm and also it serves the hot water tape in the kitchen used sometimes for anything not getting washed in the dish washer.

Doing this has reduced the power bill by about 10-15% a month. Not a lot, but also not nothing.

1 hour a day is all you need, but once a week you should run it for 5 hours to ensure you don't have to deal with legionnaires disease.

Once I have my solar panels installed, will go down to a 1.5 or 2kW element so that solar can help with additional savings. Will have to rethink the morning showers.

 

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The cottage has a 2 kW element, so I will definitely try to go smaller if possible. The peaks in the morning are killer.

We have been experimenting and manually switching off and powering up the geyser an hour before showering, it seems to work well. The geyser was powered on at 08h00 by which time we're usually producing close to 2 kW. And the batteries have gained a little bit of charge to help as well. Tomorrow we'll try to start it a bit later. We didn't want to push our luck too much.

So for the first time ever, we've only consumed 1.3 kWh from the utility, so far. The battery ran out at 04h00. Tonight I will have to close the tap a little to cater for the electric stove but once that has been replaced we might actually be able to get through the night, or at least till midnight with our nightly power usage.

 

What about heat pumps? A friend of mine with solar loves the heat pumps. With the two on his property he manages to keep consumption to around 4 - 5 kWh per day. And the 1 kW consumption is also very solar friendly.

Edited by Paul Greeff
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For the HWC, a solar unit + electric element for when the sun isn't helping out enough would be a good option to consider + lots of extra insulation on the cylinder side to have the least amount of losses, I'd suggest... also maybe speak to the elderly folks to see whether they can modify their habits, shower in the afternoon rather than the morning etc. to help out with energy saving etc.

As for your batteries, what batteries do you have? If they are lead acid, they should never run out, else you are severely shortening their lifespan, even deep cycle batteries should probably not go lower than 70 to 80% energy remaining in the cells, if you have LiFePO's then its still a good idea to not go lower than 20 to 30% energy remaining before charge being put back in the cells, if you expect a decent life out of those.

Don't take this for gospel, I'm sure others' opinions will be in direct opposition to mine on the battery end, but do your own homework and research this, batteries are a significant cost of the whole solar setup and if not treated right can have a seriously short lifespan and make the whole energy independent scenario become less than viable very quickly.

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Just a note with regards to geysers ... it generally takes around 1h20min to heat up a 150 lt with a 3 kw element ... if you choose to reduce the size of the element like I have to 1 kw so that I can run my 5 kva generator and  switch the changeover switch without having to go around switching off stuff ... then using a timer to limit the geyser operating times ... you could find yourself sleeping out with the dogs. 

It is a tricky bussiness getting the temperature settings and timer to work under all circumstances ... a trip to the beach on a Saturday morning could result in a midday cold shower ... you know that saying happy wife ... happy life ... dont say you werent warned ;) .

 

 

 

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13 hours ago, isetech said:

Just a note with regards to geysers ... it generally takes around 1h20min to heat up a 150 lt with a 3 kw element ... if you choose to reduce the size of the element like I have to 1 kw so that I can run my 5 kva generator and  switch the changeover switch without having to go around switching off stuff ... then using a timer to limit the geyser operating times ... you could find yourself sleeping out with the dogs. 

It is a tricky bussiness getting the temperature settings and timer to work under all circumstances ... a trip to the beach on a Saturday morning could result in a midday cold shower ... you know that saying happy wife ... happy life ... dont say you werent warned ;) .

True that, that is if you start from cold water tap temperature. Generally however your geyser, after a shower or 2 will still have some hot water in, so the temperature as a whole shouldn't drop to that level during the summer months. In winter...yes.

Personally only tested summer so far. I am sure I will make changes when winter comes around.

Currently my 3kW element geyser only spends around 20-30minutes to heat up the 1 geyser, which is inside the roof. The 4kW geyser spends 30-40minutes after 2 shows, but this geyser is on top of the roof so more exposed to outside cold at night.

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The physics is easy: the specific heat of water is about 4.2 kJ/kg.  This means that 4.2 kW will heat 1 kg of water by 1C in 1 second.

More practically a 3kW element will heat a 150l geyser by 1 degree in 210 seconds, or about 17C in an hour.

These numbers do of course exclude heat required to warm up the geyser itself, as well as heat losses occurring during the heating. but they are relatively small.

 

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I have a 150l and a 200l geyser, both fitted with a 2kW element. I use sonoff devices to manage the schedule.

Geyser 1 - Every day 4h00-5h30 and 15h00-16h30
Geyser 2 - Everyday 5h30-7h00 and 16h30-18h00

During during summer I only let them only go for 1hour at a time twice a day. We have warm water all day round in both showers. We are 3 people using the 150l geyser and 2 people using the 200l geyser.

 

LED lights... will change your consumption quite a bit, especially if you have outdoor lights. ROI on these is short if you replace all your lights

Add day/night sensors on your outdoor lights (HELPS IF YOU ARE FORGETFUL LIKE ME)

Geyser blanket (i don't have but it does help a lot)

Fill you kettle only to the level needed (if you are a big coffee and tea person)

Stove/Oven .... gas ... but you have this already

freezers is a pain, cause you can save quite a bit if you set the temp higher during the winter times, but who remembers this every season change.

Computers, use the sleep function, I was amazed how much power two desktop pc's can use. switch your extra monitors off when not needed

Pressure pump is on a sonoff device as well... you don't need the toilette to fill up quickly at midnight.

Maximize daytime usage, by doing washing, dishes and vacuum during the day when you have sunlight.

Throw your oil heaters in the bin, those are the death of any system.

Every time you leave the TV to go to "le jon" make sure you switch off unnecessary lights.

We also have more than one house on the property running off solar, try and get a tablet on the wall on the second property, so that the other house can also monitor power.

Damn .. I can go on forever, but different people have different lifestyle requirements.

 

We use on avg. 35kwh a day, but if we just think about usage we bring it down easily to 20kwh. unfortunately we are not always committed. Our panels are aligned so that we get a constant 35kwh a day summer and winter, I know we can generate more power in summer, but having a constant number makes life easier, and knowing that we get 35kwh a day allows us to splurge a bit on power when we don't really have to.

 

 

 

 

Edited by stoic
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  • 1 month later...
On 2021/02/09 at 11:38 AM, Paul Greeff said:

...................3. Small loads that add up to a lot of power. We still have to identify these little buggers. They're all over the place. For example, I have three fridges and a freezer, and then the fridge and freezer in the cottage, plus the fridge in the caravan. Just switching off the fridge in the caravan noticably dropped our usage over night but we're still hunting for other items to disable.

Refrigeration is often overlooked or ignored when looking for energy savings.

 

Cleaning the condensor and/or improving air circulation around the fridge can reduce the energy it consumes by 20%... or a lot more if it's a commercial underbar type fridge. Ive seen up to 40% energy saving with condensors being cleaned on commercial underbar units. Even domestic fridges have small condensor fans sometimes, check they're working and dust free.

Check the door gasket for damage and replace if necessary, also angle the fridge slightly backwards so the door has a better tendancy to close on its own.

Use your cellphone to check the internal lights switch off when the door closes.

If you fridge or freezer needs manually defrosting do so regularly, don't wait until there's thick ice built up inside it. If it needs defrosting more than once every couple of months check the door gasket and the door hinge adjustment. I've seen old fridges where the plastic washer in the hinge has broken and fallen out causing the door to drop down about 5mm and leave a thin air-gap along the top of the gasket when the door is closed and most people wouldn't be tall enought to notice this.

Check the temperature isn't set too low, if it is then thermal losses through the insulation become excessive. Don't use glass door fridges unless you really have to, they have higher thermal losses through the door than a regular fridge. If the fridge feels cold on the outside of the cabinet or it has areas on the cabinet where condensation forms, assuming the internal temp is correct then get rid of it (preferrably check it with a thermal camera if possible). Always buy a fridge with a minimum of A++ energy rating. I've also seen chest freezers where the thin aluminium internal liner has become damaged by frozen food being dropped inside it, this led to the foam in the base area becoming water logged and losing its insulation which in turn meant the compressor was running 24/7.

Locate fridges and freezers in a cool and ventilated room without direct sunlight.  I've seen a 30% energy saving where domestic fridges were in a small room with polycarbonate roof and direct sunlight from big windows and they were moved to inside the garage where it was much cooler ambient temp. This will also enormously  improve the compressor lifespan.

There's an urban myth that says it's not good to turn fridges off. I'm guessing it's because if a fridge has a slow gas leak it might leak quicker if the fridge isn't running. Ignore it, if you have a fridge that's empty don't leave it on to unnecessarily consume energy; rather run one full fridge than two half empty ones. On the one in a thousand chance your fridge does have a gas leak it will already be highly inefficient and needs fixing or replacing anyway so you've got nothing to lose in the long term.

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On 2021/02/10 at 5:29 PM, Chloe said:

Put a 1.5kW element in the geyser set to 70 put it on a timer to only heat during the peak times. Sunsynk inverters can supply power to non essentials loads. Some guys here run there geysers on the aux port on the inverter.

The non essential load supply will switch on when power is available. If you have a lot of PV panels then it can deliver a lot of power. So no need to reduce the size of your element before you see how much power is available. Those without a non essential output reduce their geyser element size so it won't overload the inverter if other loads are also on.

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1 hour ago, Richard Mackay said:

The non essential load supply will switch on when power is available. If you have a lot of PV panels then it can deliver a lot of power. So no need to reduce the size of your element before you see how much power is available. Those without a non essential output reduce their geyser element size so it won't overload the inverter if other loads are also on.

That's true but I know a lot of people who have more than one geyser and at 3/4kWh per geyser thr draw is to much even as a non essential load. 

But then again I run the entire house from my 5.5 Sunsynk inverter including the geyser, pumps and the occasional lawnmower... 

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1. So far the system works very well. I still want to change the geyser element for a smaller one, if only to reduce the current draw when it comes on at 08h30 so the little bit of solar is enough to cover the geyser element. Even though a heatpump can save a few kWh per day, it works well enough as it is that we will reevaluate this winter to see if we need to improve on it.

2. The electric stove / oven combo was replaced with an all gas Bosch. My mother is very happy with the new unit and the savings are awesome. And I am very impressed with the temperature control of the gas oven, something I was a bit worried about.

3. For the night time draw, considering we're two houses, and six people, I am happy to accept I needed the extra batteries. I'll add one more once the additional panels are done, but we're at the point where we can use 0 kWh from Eksom as long as it is a clear sunny day. Just a few more panels then we'll be good to go.

 

@Richard Mackay, the Aux output would have been very useful for the geyser, were it not for the fact the geyser is in the one house, and the inverter is in the other on the property. So the geyser is under time control. For our installation, the Aux output is a bit redundant. I'd rather repurpose it as a genny input later.

 

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This is my pet subject: the scheduling of RE power.

It's not easy to do with intelligent control (i.e by determining the available power and deploying it appropriately) It appears that with inverters that don't have a non essential output it's difficult to determine what the available power is. This puzzles me!

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Just now, Bobster said:

Doesn't the 1.5 kw geyser element mean that it draws for longer? It will make a difference to peak draw but less for draw over 24 hours. 

Thats exactly what I want to do, lower the power draw in the early morning, and late afternoon when the sun is no longer at its peak. The total power used will be almost the same, the only difference is I wont be using the battery along with solar for that first 30 to 60 min in the morning and later afternoon geyser top ups.

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4 minutes ago, Richard Mackay said:

This is my pet subject: the scheduling of RE power.

It's not easy to do with intelligent control (i.e by determining the available power and deploying it appropriately) It appears that with inverters that don't have a non essential output it's difficult to determine what the available power is. This puzzles me!

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.

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12 minutes ago, Bobster said:

Doesn't the 1.5 kw geyser element mean that it draws for longer? It will make a difference to peak draw but less for draw over 24 hours. 

Also, and one of my favourite subjects, 1.5 kw is about what a heat pump draws. Plus the heat pumps come with a timer. Mine turns on at 6, the compressor runs for about 50 minutes (in March, less in January, longer in June) and is left on until 9 but the compressor seldom runs during that interval, and then only for a few minutes. Switches back on at 12, most days the compressor runs for 10 minutes, and the wife is still showering at 8 or even 9 pm. (our geyser having a blanket) 

Because of the reduced draw we can run the heat pump on the backed loads side of the DB. 

Cons: you have to cough up for a heat pump. 

Edited by Bobster
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Very tempted to get a Sense to work out what my "by device" consumption is, the only downside seems to be the time that it takes to work out what your loads are in the house. Can take weeks from the sounds of things

https://sense.com/

 

I use the smart breakers from Robofactory for my heavy loads, they will handle up to 63A, show power consumption and use the Sonoff Ewelink software so are 100% compatible with Home Assistant.

 

My end goal is to have my Sunsynk inverter linked up to home assistant so it can make intelligent choices as to when to switch my heavy loads such as geysers, borehole etc on, based on the power it is getting from the sun and the status of my batteries. Is a project that is still in process and am still looking for the "standard grade" solution 🙂 as it all seems to be above my pay grade at the moment.  

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