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What’s the cost of a 5 minute 8.5Kw shower in 2017/2018 ?
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22-12-2017 12:37PM#1
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No, cheaper to heat by gas per liter but a greater number of liters. Even if twice the volume was used it would still be cheaper with gas as the unit rate is ⅓ the cost of electricity.
If I run the hot tap at my kitchen sink filling a liter jug till I get hot water I'll fill 6 jugs. This means when I'm finished I leave 6 liters of hot water in the pipe as wastage. This is called the dead leg.
If you have a combi boiler in the attic or downstairs you'll have a dead leg of at least 6 liters. An electric shower will only use 15 liters for a five minute shower at this time of year.
I'd argue that there's very little difference in the cost of a 5 minute shower between an electric shower & a combi boiler. Factoring in using more than 3 liters per minute with a combi boiler & the dead leg, a combi boiler could be more expensive to run then an electric shower for a 5 minute shower.
I've a shower backing onto the hot press & have a dead leg of over a liter even this close to the hot water cylinder. Heating your cylinder with gas is cheaper than electricity but you will heat a lot more than the 15 liters & the 1 liter dead leg. Then you won't be happy with 3 liters per minute coming from your cylinder so you put a shower pump on. You are now showering in 10 to 20 liters per minute.
When you look at everything together I still recon an electric shower is the cheapest option for a 5 minute shower. Your electric shower costs around 300 every 10 years in repair of replacements where using the gas boiler to heat the water would have no effect on the maintenance of the boiler
Electric showers are my business but even at that I say give me a power shower any day. My own shower pumps out 23 liters per minute. I can drain the tank in 10 minutes but I love it!
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That is a lot of south facing roof space.
It's roughly 1m² per 100w but they are getting more efficient every year.So €1800 for 3kWp. Where do you buy 2nd hand solar panels?
What other kit do you use? Are you syncing with the mains?
You're the one said 3kW, 2kW is adequate with energy conservation.
Ebay Uk because the uptake on them is much higher and there's a bigger market. Re is 5 years behind Europe in it's perceptions of it's utility.
Well I mostly DC couple because grid tied and alternating current is of little interest to me.
MorningStar charge controllers, Kraus and Naimer cam switches and Albright contactors are my only hard-won loyalties.
The rest of my personal systems are made of whatever was vaguely suitable that I could get for cheap. I buy a lot of broken kit and fix it.
I've 550W syncing with mains on a cheapo 600W GTI I wouldn't recommend.
No brainer really: Panel -> DC Isolator -> DC Powermeter -> GTI -> 3A RCBO -> AC Isolator -> AC kWh Counter & Power Meter -> Distribution Board.Why would you heat 250 to 500 litres of water a day and why heat it
to such a low temperature?
I wouldn't but one could if one wanted with 3kW of solar available
Assuming the air temp. is 15°C + 35°C = 50°C ...how hot do you want yer shower?This would mean a maximum of 500 x 4184 x 35 = 73.24 MJ
So an average output of 424 (Spring to Autumn) to 848 watts (Summer).
Pretty impressive.
I could give you the long calculation on solar azimuth, temperature derating, inverter efficiency, panel aspect, panel efficiency etc...
or you can take my word for it per 100Wp of PV you hang you'll get between 300Wh to 650Wh per day March to October.
Hence I design systems to 3X rated power in daily energy.Any pictures?
Photos? Old ones. Builder's house and all that. I'm souping up the motor and working on a friend's boat atm.
12kWh battery @ 48V
1.5kWh battery @ 12V
2.4kVA Marine Inverter Charger does the job, not worth the RRP
6kVA Low Frequency AC Coupling Inverter Charger, currently not operational.
45A MPPT charge controller derated to 37.5 due to amputated FET
45A PWM Charge controller
30A 12V PWM Charge Controller
400A Motorised 3P DC Switch-Disconnect
100A of Solar Charge Control, DC Isolators and ChangeOvers (battery / grid tie)
48VDC Distro. 350A Capable. Fused at 80A.0 -
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Sir Liamalot wrote: »You're the one said 3kW, 2kW is adequate with energy conservation.
Actually I said "Assuming that you accept that 3kW is the minimum size for a reasonable immersion element". I picked this value as it is generally accepted to be the most standard domestic immersion element size.Ebay Uk because the uptake on them is much higher and there's a bigger market. Re is 5 years behind Europe in is perceptions of it's utility.
I would not say that many people will remove PV panels that are performing well. I accept that there is the odd exception that can be picked up by those that know what they are looking for (like you). I think that you will accept that in reality there are not many people that can do this.Well I mostly DC couple because grid tied and alternating current is of little interest to me.
MorningStar charge controllers, Kraus and Naimer cam switches and Albright contactors are my only hard-won loyalties.
The rest of my personal systems are made of whatever was vaguely suitable that I could get for cheap. I buy a lot of broken kit and fix it.
I can see why this works for you. Clearly you know what you are doing and are quite passionate about this. Most people do not have this expertise or time and interest to gain this expertise.Assuming the air temp. is 15°C + 35°C = 50°C ...how hot do you want yer shower?
I'm assuming that the cold water tap temperature is about 7°C. So if I heat it by 35°C (as you suggested) then it will reach a temperature of 42°C which for a shower a bit cold, especially when you consider that there will be a further heat loss before it reaches the shower.I could give you the long calculation on solar azimuth, temperature derating, inverter efficiency, panel aspect, panel efficiency etc...
or you can take my word for it per 100Wp of PV you hang you'll get between 300W to 650W per day March to October.
A watt is a joule per second. So when you say "300 to 650W" you need to tell me how long this is for so that I can work out the energy output.
I don't know if this is 300 to 650W for a second, an hour or ten hours per day? Can you tell me how many joules per day, how many kWh per day or how many watts per hour on average? Is my earlier calculation an accurate reflection ?
My earlier calculation:
Max energy output per day 73.24 MJ
Average output of 424 (Spring to Autumn) to 848 watts (Summer).
The photos look very impressive, clearly you know what you are doing. I take it that your installation costs for labour are zero as you install them yourself and you pay less for materials as they are second hand.
My response was to GarIT who I suspect (but I am open to correction) like the vast majority of people does not have your expertise, enthusiasm or experience.
The average person with little or no technical understanding of installing PV panels to heat water will have a far longer pay back period. This is especially the case when you consider that for the vast majority of people the panels will be new and they will have to pay a specialist to install them. Add into this the fact that many of those that claim to be specialists are not that special (some may even call them chancers)
The company I am working for (we specialise in energy optimisation projects) plans to install industrial scale PV arrays in the near future, so this is an area I am interested in.0 -
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Actually I said "Assuming that you accept that 3kW is the minimum size for a reasonable immersion element". I picked this value as it is generally accepted to be the most standard domestic immersion element size.Have you any idea how much roof area is required for 3 kWp of PV panels?
I think you are working under the assumption that the solar array has to work in direct drive. This is not necessary you just need to insulate the water tank.I would not say that many people will remove PV panels that are performing well. I accept that there is the odd exception that can be picked up by those that know what they are looking for (like you).
I bought 500Wp that regularly produces 550Wp. I've a 265W was a reject because it wasn't as black as the rest (which I verified myself to be true), I've 2 x 240W that were used to test a racking system load bearing capability, that were looking for a home after testing was complete. Also have 1kWp of cracked amorphous modules (free) that are mostly working fine but just need some UV glue injected. I'm decommissioning a 150Wp module myself that has on occasion produced 120% rated because I'm upgrading to a 265Wp and there's no room for the old, which I may or may not sell depending on whether I can find a use for it.I think that you will accept that in reality there are not many people that can do this.
Point at sun, meter under load...hrmm sadly I agree.I can see why this works for you. Clearly you know what you are doing and are quite passionate about this. Most people do not have this expertise or time and interest to gain this expertise.
I wasn't recommending a DC coupled system which is what I'm building x3.
AC coupling is lossy and easy peasy. I installed mine in 1.5 days and most of that was mechanical.I'm assuming that the cold water tap temperature is about 7°C. So if I heat it by 35°C (as you suggested) then it will reach a temperature of 42°C which for a shower a bit cold, especially when you consider that there will be a further heat loss before it reaches the shower.
It takes the same energy to heat 1 litre of water 1°C. If you want hotter, then heat less volume. Most water tanks are substantially smaller than a quarter ton. It was just an example calc.A watt is a joule per second. So when you say "300 to 650W" you need to tell me how long this is for so that I can work out the energy output.
Consider the water tank a heat battery, in which case time is only relevant to offset installation heat loss.
300Wh to 600Wh per day, sorry for confusion, will correct above.
If you want specific figures try thisThe photos look very impressive, clearly you know what you are doing. I take it that your installation costs for labour are zero as you install them yourself and you pay less for materials as they are second hand.
Yurp and I'm not afraid to buy broken gear. I was expecting you to tell me the PE is too small...cos it is. There's another 10mm² PE conductor on the DC distro grounding plate outtov sight but I have to upgrade it to one size smaller than the biggest DC conductor. Which if I can resurrect the 6kVA, 18kVA surge then it'll be about 50mm² (thin wall ELVDC Cable rating not low voltage)
It's not a commissioned system although I can get it up and running in a power cut.My response was to GarIT who I suspect (but I am open to correction) like the vast majority of people does not have your expertise, enthusiasm or experience.
You asked for photos, that's what I got, it's a highly efficient system. You can simplify it by a factor of 5 if you didn't care about system losses and want to believe what the inverter/charger/charge controller manufacturers tell you.
As I say AC coupled batteryless grid tie is a no-brainer. You can buy plug and play inverters on the mainland but they're not legal here. (Very little is....brown envelope sh**e as usual)The average person with little or no technical understanding of installing PV panels to heat water will have a far longer pay back period. This is especially the case when you consider that for the vast majority of people the panels will be new and they will have to pay a specialist to install them.
Add into this the fact that many of those that claim to be specialists are not that special (some may even call them chancers)
Indeed...I fix a lot of systems "specialists" install.
I wouldn't let them turn a screw near my systems...there's a mentality of acceptable embedded losses which while it is the only economically viable way to operate commercially aggravates me no end.The company I am working for (we specialise in energy optimisation projects) plans to install industrial scale PV arrays in the near future, so this is an area I am interested in.
First agenda please build a grid tie inverter that only powers up when it is a generator. This time of year they're all running as parasitic loads in low light across 52°N.
When you do, let me know because I'll be interested.
Second agenda. Please make a batteryless DC MPPT proportional controller for water heating. Why does everyone have to use an inverter with associated losses to power a resistive element?
When you do, let me know because I'll be interested.
Third agenda. Please, please, put them on the bloomin' rooves and stop doing cheapo ground mounts competing with agriculture! :mad:0 -
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