How many solar cells should I install?

[gejohesch]

My apologies if this is not the right place to post my questions.

 

I have 2 houses connected to each other on the same compound in the Khon Kaen "jangwat". About 200 sq metres of living space (or 2000 sq ft if you prefer) in total. My electricity usage so far varies between 150 and 250 units per month so far (we are only 2 persons living there). We usually run a 18,000 BTU AC in our bedroom, for a few hours a day - that's included. We plan to install solar cells - to be green and maybe even do some savings, who knows? But we want to add a 24,000 BTU AC unit in our "common room" (60 sq metres) and we also want to cater for more usage if friends come to spend some time with us : that would add 2 other large rooms + annexes with one 24,000 BTU AC unit each. Obviously, the AC's will not be on 100% of the time.

 

Now, I am a bit at a loss when it comes to sizing up the solar cell installation we need? Can anyone give useful advice on this?

[sezze]

Wrong forum , @Crossy might come along to solve that ( theres a renewable energy topic in the forum ) .

Anyway , It is a bit difficult to say without knowing your consumption in the 1st place . the 150-250 units is pretty easy calculation , but adding a few big aircon's , that will pump up your amount of energy needed quite a lot , depending on how long they run each day .

Also , you want to feed back to the grid or just use them as you produce them ?

+/-200 units per month = +/- 1800 watt of solar panels , simple calculation is your Wp *4 to have your average daily output ( depending on angle , shadow , inverter ... , can be 3.5 to 4.5 ) .

[Crossy]

Let's move this to "Alternative Energy"

[Crossy]

Since you already have a grid supply then going "grid-tie" would enable you to reduce your power bill without breaking the bank on solar.

 

Even a couple of 350W panels and a 1kW grid-tie inverter would generate 2-3 units per day for a pretty small investment and is an easy DIY job to ease you in to the solar world.

 

There are many questions to answer, and more will come to light as you answer, there's lots of experience here so ask away.

 

A few questions to get us started:-

 

Do you require "UPS" functionality to keep your lights on even if the grid goes out?

 

Are you going to DIY this or get in a contractor?

How much space do you have for panels?

Where are you going to put them, house roof, car port, ground mount?

 

Task A. Is to work out your current and future daily power usage in kWh.

 

You can reasonably assume that an A/C will use very roughly (BTU rating)/30 kWh per hour of operation if it's correctly sized and you're not keeping pet penguins.

 

 

[kiteman9]

 

[gejohesch]

12 hours ago, Crossy said:

Since you already have a grid supply then going "grid-tie" would enable you to reduce your power bill without breaking the bank on solar.

 

Even a couple of 350W panels and a 1kW grid-tie inverter would generate 2-3 units per day for a pretty small investment and is an easy DIY job to ease you in to the solar world.

 

There are many questions to answer, and more will come to light as you answer, there's lots of experience here so ask away.

 

A few questions to get us started:-

 

Do you require "UPS" functionality to keep your lights on even if the grid goes out?

 

Are you going to DIY this or get in a contractor?

How much space do you have for panels?

Where are you going to put them, house roof, car port, ground mount?

 

Task A. Is to work out your current and future daily power usage in kWh.

 

You can reasonably assume that an A/C will use very roughly (BTU rating)/30 kWh per hour of operation if it's correctly sized and you're not keeping pet penguins.

 

 

Thanks for your constructive help! I was thinking indeed of a grid-tie (or “on-grid”) system whereby the solar panels would provide power during the day and we would use the grid during the night. Hence no need of a battery system which would be much more expensive.

 

Now to your questions:

 

 1 Do you require "UPS" functionality to keep your lights on even if the grid goes out?

I guess the answer is NO, as this would probably mean much more equipment = $$$. We are willing to accept the occasional power cuts (not that often in our village). Note, it’s not that we are “cheapies” but there are so many other things to sort out in our compound, the $$$ we save on solar we can use nicely somewhere else.

 

 2 Are you going to DIY this or get in a contractor?

NO. I cannot see myself doing it. So, contractor it will be.

 

3 How much space do you have for panels? Where are you going to put them, house roof, car port, ground mount?

Thinking of one of the roofs. We have plenty of space and choice between our 2 houses (they are separated by a courtyard 4 metres wide). Maybe also, we could consider the roof on top of the garage, right by the side of the houses. Note: there are no obstructions anywhere, our compound is well clear off the neighbours.

 

 4 Task A. Is to work out your current and future daily power usage in kWh.

We use roughly 200-250 kWh per month. That goes towards 350 kWh when we have a lot of work being done in the house, like welding etc.

We are aiming at adding 3 AC units of 24,000 BTU/hour each. We don’t run them during the night. Lots of people do, but not us. Too cold, too noisy also. We cool the rooms well during the day and use fans at night.

 

I’ve read somewhere (Thailand statistics) that a 12,000 BTU AC consumes on average 0.7 units (kWh) per hour if set for 26 degrees C and external temperature 35 degrees C. Up to 0.8 units per hour if 41 degrees C external. Averaging that to 0.75 units/hour and scaling up from 12,000 BTU, I get 365 kWh per month for a 24,000 BTU unit. That’s assuming switching the AC 8 hours per day (the rooms are not occupied all the time during the day after all).

 

This brings me to a total of: 200 or 250 current + 3* 365 additional = 1545 to 1595 kWh per month. Let’s then just say we aim at a solar cell installation providing 1500 kWh per month.

 

 5 You can reasonably assume that an A/C will use very roughly (BTU rating)/30 kWh per hour of operation if it's correctly sized and you're not keeping pet penguins.

I’m puzzled here. Taking a 24,000 BTU unit, dividing by 30 gives me 800 kW per hour of operation. Hence if 8 hours usage per day, close to 200,000 kWh per month. Have you skipped a 1,000 factor somewhere? If so, it would be ca. 200 kWh (PEA “units”) per month per 24,000 BTU AC unit, i.e. much less than the 365 kWh I calculated above?

 

I have another question, if I may. Would it not be sensible to start with a smallish installation and add to it later on if necessary?

 

And ….. No, we are not keeping penguins, hahaha! We just like to keep comfortably cool, and keep our drinks cool too!

[Crossy]

Yeah, I think a factor of 1,000 got missed somewhere. Your 24,000 BTU A/C will use 2.4kW when the compressor is running, at 30% duty cycle (which depends upon the ambient temperature and how under-sized the unit is) that's 0.8 kWh per hour of use.

 

You have to be careful going grid-tie unless you are joining the official system as "spinning the meter backwards" (net metering) is technically illegal (so avoid the meter reader seeing it).

 

Definitely a good idea to start small and see how it goes. The big string inverters are more efficient but starting with 3 panels and a 1kW inverter will show measurable savings (3 units a day ish).

 

1,500 kWh per month - 50 units per day - you're looking at 50 x 300W panels with the associated inverters and an unhappy PEA (they are going to notice).

 

The garage / car port is probably the best starting point, no real worries about leaks and it's not waaay up in the air.

[2BOB]

Try  EYECANDI SOLAR CHIANG MAI Shaun is a american and one of the biggest in chiang mai. very noligable .

[gejohesch]

2 hours ago, Crossy said:

Yeah, I think a factor of 1,000 got missed somewhere. Your 24,000 BTU A/C will use 2.4kW when the compressor is running, at 30% duty cycle (which depends upon the ambient temperature and how under-sized the unit is) that's 0.8 kWh per hour of use.

 

You have to be careful going grid-tie unless you are joining the official system as "spinning the meter backwards" (net metering) is technically illegal (so avoid the meter reader seeing it).

 

Definitely a good idea to start small and see how it goes. The big string inverters are more efficient but starting with 3 panels and a 1kW inverter will show measurable savings (3 units a day ish).

 

1,500 kWh per month - 50 units per day - you're looking at 50 x 300W panels with the associated inverters and an unhappy PEA (they are going to notice).

 

The garage / car port is probably the best starting point, no real worries about leaks and it's not waaay up in the air.

50 panels of 350 W each! I did not think a second it could be that much! It's just not feasible on a private basis, it sounds more like an industrial-scale installation!

 

Honestly, I find all that very confusing (and I had a good education in maths and physics!). Maybe the best is to install the AC's, run the house for a couple of months, see where we lend in terms of consumption, and only then revisit the required size of a potential solar cell installation.

[sezze]

1500kW /m is a lot also , setting you back 7000-8000 baht every month , instead of your 1000-1500 bills right now . You got a 12000 btu now , and you are adding 2 24000 btu units , making your consumption 5 fold .

[gejohesch]

23 minutes ago, sezze said:

1500kW /m is a lot also , setting you back 7000-8000 baht every month , instead of your 1000-1500 bills right now . You got a 12000 btu now , and you are adding 2 24000 btu units , making your consumption 5 fold .

Yeah, appreciate that. However, we've got 18,000 BTU now (not 12,000) and we run a few other usual things like light bulbs, coffee machine, a bit of music in the house and, maybe not that usual, an electric oven which I use 2 or 3 times a week to cook western food. So, adding 2 units of 24,000 BTU's each would not exactly be like a 5 fold step-up, especially if a good half of the whole living space is not fully used on a daily basis (it's more like accommodation for occasional guests). But I get your point.

 

As said, I think we'll install the extra AC's and watch the consumption over a few months to get a better feeling. 

Maybe also, a good idea would be to set up 2 separate solar cell systems, one for each of the 2 houses?

[Crossy]

We have 20 panels on our car-port (8 x 300W plus 12 x 345W totalling around 6.5kWP) running grid-tie and (illegally) net-metering, have a look at this thread 

https://forum.thaivisa.com/topic/1120934-how-about-a-solar-car-port-on-a-budget/

 

That generates around 24kWh per day although it varies with the weather of course.

 

Probably going to add another 3.5kWP this year, anything over 10kWP single-phase is supposed to be covered by the industrial installation rules.

 

We actually use about 40-60kWh per day depending how many visitors we have staying so we get around 50% of our electrical energy from the solar.

 

We only run the A/C at night except on really hot days when I'm working from home when the 24,000BTU inverter in the lounge/office gets fired up, we have a "base-load" of about 1.5kW (36kWh per day on it's own) consisting of the koi pond (Madam's fish have a good life), the pool pump and fridge/freezers along with a couple of servers and 3 PCs.

 

[sezze]

Yes , i think it is a good option , since we are only guessing your consumption . Having 2 more aircons , don't mean you use both at the same time . And since 24000 btu aircons , do use some serious power on daily basis , the calculation would be way off . If you use only 1 at a time and a few hours a day , can be that your consumption wouldn't go to 1500 kWh , but maybe only to 500-700 kWh , which is much easier to replace big part of solar . All comes down to your consumption , you want to replace big power , you need big money also , small consumption small money ...

[sezze]

2 minutes ago, Crossy said:

We have 20 panels on our car-port (8 x 300W plus 12 x 345W totalling around 6.5kWP) running grid-tie and (illegally) net-metering, have a look at this thread 

https://forum.thaivisa.com/topic/1120934-how-about-a-solar-car-port-on-a-budget/

 

That generates around 24kWh per day although it varies with the weather of course.

 

Probably going to add another 3.5kWP this year, anything over 10kWP single-phase is supposed to be covered by the industrial installation rules.

 

We actually use about 40-60kWh per day so we get around 50% of our electrical energy from the solar.

 

We only run the A/C at night except on really hot days when I'm working from home when the 24,000BTU inverter in the lounge/office gets fired up, we have a "base-load" of about 1.5kW consisting of the koi pond (Madam's fish have a good life), the pool pump and fridge/freezers along with a couple of servers and 3 PCs.

 

When talking new install , also to remind that most panels nowadays are 400-500 watt panels , requiring less space/panels .

[brianthainess]

Would that not depend on how many deep cell batterys you want to keep charged ? 

[BritManToo]

16 hours ago, gejohesch said:

This brings me to a total of: 200 or 250 current + 3* 365 additional = 1545 to 1595 kWh per month. Let’s then just say we aim at a solar cell installation providing 1500 kWh per month.

40-50 x 340w panels (2m x 1m) ...... 150,000bht that's a big install.

 

I have 5 (340w) panels that produce around 130kwh/month (15,000bht)

And 2x Suoer GTIs (2,500bht each).

That reduces my household bill to 800bht/month in summer and 400bht/month in winter.

[Crossy]

1 hour ago, brianthainess said:

Would that not depend on how many deep cell batterys you want to keep charged ? 

 

Not with a grid-tie system, it has no batteries.

 

[gejohesch]

8 hours ago, sezze said:

When talking new install , also to remind that most panels nowadays are 400-500 watt panels , requiring less space/panels .

Good point. Thanks

[gejohesch]

15 hours ago, gejohesch said:

......

As said, I think we'll install the extra AC's and watch the consumption over a few months to get a better feeling. 

Maybe also, a good idea would be to set up 2 separate solar cell systems, one for each of the 2 houses?

Developing on that, my idea would be to separate the section of the compound we use on a regular basis and cover that with solar power, and leave the other section which is used less frequently (e.g. when we have visitors staying in) and take that less frequent power consumption from the grid. No need to spend money on a solar installation that would only occasionally be of use.

The trick is of course to "separate" these "two sections", it's a nice concept (I think) but the physical reality is a bit different. For example, we use a lot a big washing machine that is located in the part of the compound which I would designate as "less frequent usage". Not being a pro, I would still imagine that it would all boil down to wiring / connecting appropriately - distances all around the 2 houses + inner courtyard are never really that much. 

[gejohesch]

4 hours ago, BritManToo said:

40-50 x 340w panels (2m x 1m) ...... 150,000bht that's a big install.

 

I have 5 (340w) panels that produce around 130kwh/month (15,000bht)

And 2x Suoer GTIs (2,500bht each).

That reduces my household bill to 800bht/month in summer and 400bht/month in winter.

Thanks for your input. It's good to have a clear and simple case in mind. Makes it possible to scale up or down according to one's needs.

[DTL2014]

ive done this calculation..i have 2 properties . 1 bill is 17,000 -we can put 34 panels up for a 15kw system.This will approx cut the bill by 50%

my second property elec bill 26,000. 45 panels 20kw system....good luck . i see SCG are doing promotion at the moment. I got my quote from KPG solar, who have teamed up with sunsear in phuket