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Forum Index : Microcontroller and PC projects : H/W system with 6,6 kW solar PV in WA, do I need a solar H/W panel?
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| Boppa Guru  Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I know our electricity bill is frugal compared to many (I have seen people on here and elsewhere throwing around 20-30kwhrs a DAY in usage- to me that's plain insane!) but I lived offgrid for nearly a decade and old habits die hard (anything not in use is switched off at the powerpoint etc) We have two tv sets going 3-6 hours a night, my laptop runs 24/7, with two people living here... We only use the aircon on hot days, but it is left on on hot days on the timer, just to keep the cats happy (they are getting old and don't tolerate the heat well anymore- the oldest is 19, the other two 17...)- speaking of which, during winter the oldest has a 'pet electric blanket' 40w adjustable temp- which is basically on 24/7 during winter... We got electric booster solar HWS (booster stays off at the breaker except if there are several days of continuous rain in winter) and an electric stove  We use on average 7.03kwhr a day in a 3 bedroom house..., with the solar system giving us 17kwhrs a day in winter (its up at 30kwhrs a day in summer- that's the winter bill) |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3010 |
20kWh per day is about my usage (in the spring/summer/fall in Nova Scotia) with oil heat and electric HW, and at $.15/kWh or $3 a day, I don't feel it's worth much in dollars or effort to try to reduce it drastically. I would barely lift a finger to try to save $2 a day, and certainly wouldn't go around turning things off and on every day. People who use AC in Arizona in the summer are in an entirely different situation--fortunately they have an abundance of solar and can economically address their problem even with the relatively (very) high cost of solar panel installation. A few years ago I think it was received wisdom that you could not economically use solar PV to run air conditioning (panel output - AC conversion < solar gain)--but times have changed. Edited 2019-10-14 23:47 by lizby PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
I've noticed that out the US way seems to be horribly high to install, one person I was talking to recently was quoted at $12g US for a 3kw system fully installed)- my system is a couple of years old now, and cost me $4g Au fully installed for a 6kw system (that's about $2800 US), the same mob are now selling the same system but with 2 extra panels- for $300Au less... We bought a brand new inverter split system, it can cool the entire house (cost us a bit more to have it installed where we wanted it), but it can have the cooling air directed by doors to either the lounge/dining/kitchen, or to the three bedrooms- or both (it runs a bit harder doing it all)- but if we leave it on the timer from 10am to 3pm, it doesn't cost us a cent to run it- in fact we still have 3/4 of the panel output going to the grid even with the aircon running |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577 |
[quote] I know our electricity bill is frugal compared to many (I have seen people on here and elsewhere throwing around 20-30kwhrs a DAY in usage- to me that's plain insane!) [/quote] I have been working out our consumption the last week or so and it's around 35 Kwh a day and I'm thinking how good and unusual that is. Winter and summer we use 60-70Kwh a day easily. Water heating in winter can easy be 4 Kwh a day just to bring the incoming water temp from the <10o C it come in at to the summer temps of more like high 20's. Then it can easily got from 12 -20 Kwh to heat the water in total. I have a septic pump that pulls another 3 Kwh a day and there is no turning that off or minimising it and then we get to the only source of heating/ cooling which is the AC. With winter temps here easily in the Minus in winter and a week of 40 in summer, it's far more a necessity than a luxury. [quote] but I lived offgrid for nearly a decade and old habits die hard (anything not in use is switched off at the powerpoint etc)[/quote] Off grid that may be very wise. with me, even if it saved 1 Kwh a day which I highly doubt, that's not going to make a scrap of difference to my overall consumption. [quote] We have two tv sets going 3-6 hours a night, my laptop runs 24/7, with two people living here... [/quote] And that's a big difference to even having a septic pump running 24/7. Does not compare to electric stove and hot water even now when I haven't hit the AC for weeks. If I look at my power meter, normally it's just creeping along. When the AC and the water heater are running, thing looks like it's going to go into orbit. It's not lights or TV, computers, the fish tank or the 10 plug in power packs around the place that really have any influence on our consumption, the hot water alone puts them all to shame. Likewise, an hour with the AC running hard pulling almost 2 Kw across 3 phases..... [quote] just to keep the cats happy (they are getting old and don't tolerate the heat well anymore- the oldest is 19, the other two 17...)[/quote] One of my original and dearly loved Puss's is sitting at my feet now having finally got off my lap. She's 14 and I don't think I'll have her come the weekend. She has kidney failure and after spending a considerable fortune at the university vet, there is nothing more than can be done. I have been spoiling her as much as I can this last week but shes now starting to not eat and that's the writing on the wall. I'm not right in the head at the best of times and have no problem beating people who deserve it to a pulp but when it comes to animals, especially ones I have had so long, I'm a pathetic mess. We have 3 other cats, 2 of which are also quite old and a 3 Yo border collie and these will be the last I have. I can't take loosing them anymore. Just not emotionally up to it. I feel sick in my stomach today knowing what's coming and I can't do anything about it. [quote] - speaking of which, during winter the oldest has a 'pet electric blanket' 40w adjustable temp- which is basically on 24/7 during winter... [/quote] I got a couple of these for my Puss's in autumn and put them in cardboard boxes I laid on their side on the back verandah up on a table. They have to stay outside because a couple are quite dirty inside and I'm not having the place ruined and befouled no matter how much I love them. They loved their Boxes and were always in them. I put towels over the top to make a little door as well as insulate them a bit and they were always in them. My wife bought some fluffy cat bed things which I'd have slept in if I could fit but like a meme I saw recently, they preferred the boxes and the cat beds were a waste of money. The boxes are very toasty warm and I think they would have been more cosy in their heated boxes than they would have been inside anyway as I only have the air set to 18 at night. I really couldn't give a rats crack how much power the heaters use. They are worth that to me 100 times over and in the grand scheme of things, it's tiddly winks anyway. Certainly nothing in comparison to the couple of grand + I've spent on vets bills last couple of months. [quote] We use on average 7.03kwhr a day in a 3 bedroom house..., with the solar system giving us 17kwhrs a day in winter (its up at 30kwhrs a day in summer- that's the winter bill)[/quote] Now THAT is insane to me! :0) 7 KWH Wouldn't even cover my hot water and we don't use much water overall anyway. There are a lot of factors in power useage including appliance and location even before you get to how many people in the house. of course if one is using gas to heat their hot water, then one is comparing apples and oranges to start with. I don't worry much about what we use other than to take an interest. The reason for my solar obsession has been exactly this, to use what we want and not have to worry. The total I have spent on doing my solar would give me change from what 2 quarter's bills would be so we are now laughing. If I can take the winter heating load for the most part off the AC, then we will really be using next to nothing from the grid. Edited 2019-10-15 09:07 by Davo99 |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577 |
I am exactly the same. I can't budget to $2 a day or a lot more. Spend a lot more than that on an impulse spend to sit and have coffee and something to eat when we go to the shops or just down to the hardware store in their cafeteria. The thing here is that half my power bill now is made up of service and "supply" charges I can't do anything about. They screw me either way. Like water that they want me to save. WHY? I'm spending more on their fees than I am on what I use so in fact, the more water I use the cheaper it becomes. If I'm using less than it's less strain on the infrastructure so how about giving me a discount for that to encourage me to use less because that's the real cost to me. Exactly my situation. Don't try to spare the AC one bit to make us comfortable. It's all but free less the wear and tear on the system... which is getting well toward it's use by Date. I installed solar at very little cost but it was an investment in comfort and peace of mind. With the predicted power outages this and summers ahead, I'm going to adjust my setups to allow for some off grid power and be self reliant at least enough to keep some fridges running. If I need more power or through the night I can fire up a genny ( Hoping to get a 10 Kw unit I have made an offer on) which will give me everything but AC atm. They also said that PV water heating wasn't worth it but now the tides have turned. Direct water heating is more exy and far less efficient from the POV it only does one thing, heat water. When the PV has heated your water it can do other things and probably was when the water was warming up anyway. Aside from that, plumbing is a pain in the arse compared to running wires. Seems to me these days they make plumbing fittings so as to omit pieces that you could go straight from this to that in one go and make it so you have to use 6 fittings where you could use just one.... If they made the damn thing! |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577 |
Spoke to my mate yesterday and remembered to question him about this. In summary he said that anything with a moving part or a motor is never going to be as dependable as something solid state, IE, a heating element. He also said most people can change a hot water element in minutes. simple and easy job and the part is worth well under $50. He said not much to go wrong with gas either, generally the pilot light or valve and they are not overly expensive or take much to diagnose or replace either. He said it takes a whole load longer to even begin to Diagnose a heat pump fault and the minute it needs a part, the cost in time and labour will eat up years of savings on power. Said electric elements can be had from any electrical supplier, heat pump parts can take weeks to get from the manufacturer. That's a big reason he does not recommend them in commercial applications unless they can afford to have extra installed as redundancy. He said generally the backup he recommends is gas anyway. He said also needs to be remembered that heat pumps cost 3-4X more than the electric/ gas heaters in the first place so you have to recover that before you get ahead and for most people, that's a very questionable scenario if the heat pumps will run long enough. I think I have gone the right way and would be for many others too. Instead of putting the money into a heat pump, put it into solar PV if you don't already have it. If you do you could look at upgrading or just be content you are probably saving more on HW than what a heat pump would gain you anyway. I have already recovered my winter power use and am having to partially disconnect my inverters because I am making too much power atm and have no use for it. Last week I have left the water heater on constantly and not worried about the voltage relay and I'm still 123 Kwh up in 4 days although wife and I were away and it was only my daughter here..... which probably meant the consumption was up on what it would have been had we been here walking round behind her switching everything off. Least I don't have to cause friction by complaining about it atm. I just turn things off as a life long habit that dies hard and say nothing. :0) |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3010 |
I know you are talking about heating water, but for heating air, the initial cost difference is even greater. Here in Nova Scotia at this time of year, I can heat up my finished, insulated 19' x 19' barn room with a $25CAN 1500W 125V heater (which I can turn on with my phone while still in the house) when the outside temperature is 5C (though I sometimes turn on a second heater to speed up the process). Friends say that the likely professionally installed cost of a ductless mini-split heat pump, 12000BTU, is above $3,000CAN. So 50-100 times the installation cost of doing it with off-the-shelf space heaters. But the heat pump also provides cooling on the several dozen days in the summer when we need it. I can get a window AC unit for around $200CAN, but I'd need to cut a hole in the wall to install it. My plan is to go with the mini-split anyway, for convenience, buying the unit in the US this winter for $700US, and doing most of the installation myself with a helper. I'll need an electrician to legally connect the wires I've run, and an AC guy to flare and connect the tubes and set the proper vacuum. I'm hoping it won't cost me over $1,300CAN. For the use I make of it, I probably won't recover the cost in operating cost savings. Why do I want to be in that room? The view:  And sometimes the visitors:  PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| Paul_L Guru Joined: 03/03/2016 Location: United StatesPosts: 769 |
@lizby - that's a cute little birdie! Resistance heaters are 100% efficient so the 1500 W heater produces 5118 btu/hr. A 12000 btu heat pump will pump 2.34 times the heat while consuming as little as 870 W of electrical power. That means the resistance heater uses 2.68 times the electrical power compared to the heat pump. In the Nova Scotia climate, considering that you spend the winter elsewhere, it will probably take about 25 years to reduce your electric bill by the price of the heat pump. If you ever do decide to stay in Nova Scotia for the winter the heat pump would pay for itself in about two years. If you bring a split system heat pump back with you when you return to Nova Scotia next fall you probably won't need either an electrician or a refrigeration guy. The split system air handler and compressor unit will both plug into 15 Ampere 120 vac outlets just like your resistance heaters. The freon line set, air handler and compressor unit are all pre-charged with freon and the line set connectors incorporate spring loaded valves, so you just screw them together. Hanging the air handler on the wall is easy. The compressor unit can be placed on a prefabbed concrete slab. It's an easy job. Paul in NY |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3010 |
As I understand it, for legal installation the system needs an external disconnect, and must be wired to the panel. I am capable of doing it (and plan to run the wires), but expect to get a permit, which requires participation of the electrician. The system is pre-charged, but I understand that the tubes need to be cut and flared, and that the vacuum should be adjusted to the actual distance of the run (only 3-4 feet compared to the 16 feet it is pre-charged for). It's a small system, so I plan to be able to hang the external part off the barn wall. PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
A lot of our savings was the solar HWS, which is actually that old now it is likely to need the tank replacing soon- all of the last year,it had the booster turned on for maybe 4-7 days total So that's one reason our elec usage is that low, free from the sun hot water... Luckily we rarely get snow in Qld (mostly) and never where I am,so heating really isn't an issue here, it's more cooling from BOM One advantage is that with our plan, and with our far more production than usage, our bills usually hover between $10 a quarter, and negative bills (where we actually get money back from them- deposited in our bank account lol- we have it set up for direct debit, and when they owe us money they just put it in the account they take it out of when we owe them- no 'credits' or other garbage)  That's the elec bill before last |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3010 |
Love the way you get dinged with a sales tax even when you're getting money back. PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577 |
I have never heard of that. The systems are usually charged for UP TO a certain generous distance and then you have to add gas charge OVER that run length to make up for the capacity of the gas volume in the Pipework and maintain working pressures in the system. The Lines are Vacced not according to distance but to remove Moisture and the Air (gas) which is not the refrigerant. The length of the run is irrelevant. You vac down as low as you can regardless. Generally the Vac pump is left running for some time after the pipe is vacced down which only takes minutes normally to boil off any moisture which will phase change from a liquid to a gas at about 1000X expansion. You do this after you have made all the connections through the valves on the unit. The refrigerant charge is kept in the condenser/ outdoor unit until the rest of the ( new) lines are properly evacuated. Once that is done generally a gauge is left connected for some time to test for leaks in that the Vac does not diminish. Another way of doing this is to pressurise with Nitrogen and check the lines maintain pressure. Once that is done the Charge is let out of the unit into the pipes and to the evaporator which has also been vacced Down with the rest of the system. From there the unit is run, pressures on the low and High side checked to be in spec and good to go. If pressures are out, especially if installing a used unit, gas is added as needed. I have done a lot of car AC and I fudge things a bit. Instead of Vaccing down when I don't have my pump, I simply Fill the system with gas a couple of times to purge it and then give it a flush by Pulling in gas on the low side with the compressor running and let it bleed out before re entering the pump. I don't use R-134, I use LPG or pro-paaaane for the Americans. On 134 Systems the charge is about half that of the regular gas and rather than weigh it in I do it by reading the pressures on the low and High side and checking the air output temp. Lots of people get all funny about the idea of using a flammable gas in their AC but don't realise how little it is and that all the new Gasses ARE Glorified LPG which is supposedly drier and better filtered. The results I have had with regular LPG are far better than that I can get out the same system with R-134. Of course being paranoid about a couple of hundred grams of gas at the front of the car is a bit ironic when there is 50+kg of petrol sitting at the back of the car. :0) I did the AC on my truck because the Mrs complained it didn't work very well. Charged it up before we went north to the sub tropics and then all she did was complain she was freezing and the thing wouldn't turn down low enough not to be too cold. It's quite amazing how cold it will get now. I have measured 35oC ambient temps with the discharge from the evaporator at 2 oc at full fan speed. Wouldn't come close to that before. Did get a blockage in the evaporator Drain and the amount of water it was condensing when we drove through a rain storm one time was incredible. She was catching it in a large paper drink cup and having to empty it about every 4.5 Minutes. Cleaned it out and the next stop with a long Zip tie and all was good. Could have got enough water out the thing to survive for a couple of days with an hours running! The systems have a Receiver/ drier built in so I let that remove anything in the gas that shouldn't be there but I really doubt there is much. When you ever see water droplets coming out of a gas burner or hear of the jets getting clogged? I think the " refining" of the LPG gas is more marketing and price hiking than anything. I have had no problems at all so far with any of the cars I have done and everyone comments how the system works better than new. Only thing to check if the system has had a leak or damage is there is still enough oil in there. I often put a bit in for good measure. I have been thinking to get some parts and make up a diesel engine driven AC. Depending on the actual unit, most car AC systems are equal in output to a mid size home split system anyway. With the addition of an RX Valve I could make the thing reverse Cycle. Using the waste heat from the engine feeding into the condenser side, The thing could be REALLY efficient on heating regardless of ambient temp. Using a water cooled engine you could feed the exhaust back through the Condenser and have the hot water piped to another location. On another forum I look at, people set up Co-gen systems to give them power from a generator and heat from the engine driving it. Very cheap and efficient when burning waste oil in a Diesel engine. Wouldn't be hard to add a compressor to the driven loads for the AC. |
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| Boppa Guru Joined: 08/11/2016 Location: AustraliaPosts: 814 |
They certainly do it in some Davo, including the new one we had installed here Installer didn't have anything except the vacuum pump, and the outside compressor housing had the premetered charge already installed inside it I was a bit puzzled myself as I have done thousands of AC recharges in car myself (auto sparky being one of my trades) and expected to see a charge bottle LOL Pregassed split AC has a description and some examples of models fitted with the precharge |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1577 |
Umm, that's what I was saying, or at least trying to.  What I meant to say I never heard of, was adjusting the vac to the length of pipe. You pull as much vac as you can, there is no adjustment of vac for the run length. You pull it low as you can regardless. The units are pre charged up to a certain pipe run length. If you go MORE than that, then you have to add gas but up to the length they specify, there is enough gas in the units as they come. All you need to do is run the pipe, Vac everything down and open the valves to let the charge into the system and all good to go. When you uninstall them, you close one valve and pump the system down back into the condenser unit and all the gas is contained back in there. |
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| lizby Guru Joined: 17/05/2016 Location: United StatesPosts: 3010 |
Thanks for the explanation. I had misunderstood what I had read about the installation process, or had conflated the vac-cing with the need to flare the pipes if you cut them. Another reason (for me) to have a professional AC guy do the vacuum line hookup. PicoMite, Armmite F4, SensorKits, MMBasic Hardware, Games, etc. on fruitoftheshed |
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