## How many watts of solar would I need?

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If we have a Fan, TV, Light and Iron press in my house How many watts of solar would we need?

average calculation,

One day load of Fan = 60 W * 15 H = 900 WH

One day load of TV  = 50 W * 15 H = 750 WH

One day load of Light = 10 W * 8 H = 80 WH

One day load of Iron Press * 1000 W * 1 H = 1000 WH

Total load for a day = 900 + 750 + 80 + 1000 = 2730 WH

are there such capacity 2730 available  in market ?

Last Edited: Sat. Jul 25, 2020 - 06:01 AM

You only need 10W of light in your whole house?---what kind of bulbs are you using?

The cells put out watts, not wh---you have to determine how many hours they will run, or maybe charge batteries (with batteries you can supply more watts than the cells can provide, for a shorter time (total wh)).  You can have a small panel on your roof, or an acre of cells behind your house---how much \$\$\$ will/can you spend.  Have you looked at any online solar calculators--there are many.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

avrcandies wrote:

You only need 10W of light in your whole house?---what kind of bulbs are you using?

I use five lights in my house 230V AC, 50 Hz, 10 watts but I used only one light for calculation and wh means watt per hours

Example : We have Fan, TV, one Light and Iron press in house. Fan run for 15 hours per day , TV run for 15 hours per day, Light  run for 8 hours per day and Iron press run for 1 hours per day

Last Edited: Sat. Jul 25, 2020 - 07:53 AM

Where do you live. (difference between daylight hours between summer and (dark) winter)

Can you trust that the sun shine everyday?

Do you plan on putting power on the grid and take some back in the evening ? (else you also need at battery and then no a simple calculation)

This page show the production in DK (click on history and you can follow the solar production over the day )

https://en.energinet.dk

wh means watt per hours

You will be sadly disappointed when you get your electric bill !!

A watt-hour (Wh)  is a multiplier==>  watts*hours   For example, 8 watts used constantly for 7 hours consumes 56 Wh

Notice 56 Wh is not watts per hours.   Also notice, the units of Watts/hr is somewhat meaningless, though allowable, just like meters/joule*ohm  is a "valid" unit for someone's crazy equation.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Sat. Jul 25, 2020 - 09:03 AM

Surely you've observed that different solar installations have differing number of PV panels? More panels = more Watts. Then you need an inverter. If you want to run everything only on solar, then you'll need a system that can deliver in excess of the total load. According to your numbers, your max load is 1120W. Thus you need a system that can deliver more than that number as weather and season affect the actual amount you can harvest.

sparrow2 wrote:

Where do you live. (difference between daylight hours between summer and (dark) winter)

Can you trust that the sun shine everyday?

Do you plan on putting power on the grid and take some back in the evening ? (else you also need at battery and then no a simple calculation)

There is not the same sunlight every day, sometimes less then sometimes more I live in India where around 10 hours sunlight remains in summer while 5 hours sunlight remains in winter.

Last Edited: Sat. Jul 25, 2020 - 09:11 AM

Kartman wrote:

Then you need an inverter. If you want to run everything only on solar, then you'll need a system that can deliver in excess of the total load. According to your numbers, your max load is 1120W. Thus you need a system that can deliver more than that number as weather and season affect the actual amount you can harvest.

Let's say we have maximum load of 1120 W.

1. How many watts solar panel do we need for house ?

2. How many PVI battery do we need ?

3. How many watts inverter do we need ?

Last Edited: Sat. Jul 25, 2020 - 09:24 AM

ansh11 wrote:
One day load of Iron Press * 1000 W * 1 H = 1000 WH

This is the dominant load but I imagine there is a thermostat involved, therefore the 1000W is probably only 300W once averaged out.

Did you miss out any refrigeration equipment ?

Last Edited: Sat. Jul 25, 2020 - 09:42 AM

is the Iron press really 1000W for one hour, or 2000W for 1/2. (important for the inverter size, or perhaps it can run directly on the DC output).

what is the voltage of your equipment ?

#9 for me it mostly sounds like a working stand, for something like iron lables on T'shirts, not a home.

Do you need the Iron to work when it's dark ?

Last Edited: Sat. Jul 25, 2020 - 09:57 AM

So, if you want to capture ~3000Wh of solar energy in 5 hours, the solar charging system needs to produce at least 3000/5 = 600Wh. That however assumes a system with 100% conversion efficiency and cheap solar chargers are nowhere near that efficient, maybe 60%, so you need 1000Wh of panels. If you can afford a better charger (e.g. MPPT) with greater conversion efficiency, you might get by with fewer panels.

The more battery capacity you have, the more dull days you can survive. But if you don't match the average system capacity (in the worst season) to your average consumption, you will slowly deplete any spare storage capacity. Winter tends to last for months.

You can't take more energy than the sun provides on any particular day, and you can't consume more than your battery storage capacity. It doesn't matter if the sun shines for 15 hours a day in summer, if you don't have the system capacity to capture and store it. **

A common mono-crystalline PV panel might provide up to 200Wh of solar energy, so you'd need 5 of these to produce 1000Wh. But don't forget the conversion losses in the charger.

If a standard lead acid battery is rated at 12V and 100Ah, that's a storage capacity of 1200Wh. But you need to take care with maximum charge and discharge rates. If you want to charge it in 5 hours, you need to provide, and it needs to be able to handle, 12V at 20A

You need to determine your maximum load at any one time, e.g. with everything switched on. That will determine your maximum battery discharge rate and required mains inverter rating. Again, inverters are not perfectly efficient. From your figures the max discharge rate is 1000W for the iron, plus the lighting to actually see what you're ironing. The battery discharge would be 1000/12V = 80A. That's a pretty big number, when poor cabling and short circuits can cause fires !

I don't know what is available to purchase in your market and what payback time (in years) you want to achieve. If you buy cheap (poly-crystalline) PV panels, a cheap PWM charger, and a cheap inverter, your average numbers will be disappointing.

** It's interesting to note that grid-scale renewable energy (solar, wind) production will continue to need reliable (coal, gas, nuclear) baseload generation on standby until a new generation of battery (or other) technology is developed to provide acceptable cost and storage density.

I guess this is to avoid a noisy generator! (And a cheap 2 stroke generator could probably be the backup for when it rain).

** It's interesting to note that grid-scale renewable energy (solar, wind) production will continue to need reliable (coal, gas, nuclear) baseload generation on standby until a new generation of battery (or other) technology is developed to provide acceptable cost and storage density

You are correct, but you forget hydroelectricity, whey hold back the water when we don't need the power.

And we also have a lot of small power plants that run on wood, that make local heat, but also electricity

One big question will also be can you angle the panels as you please? and avoid shade ?

If you follow the sun you will get 30-40% more energy out of the same panels.

When you say "a least" 5 hours of sun, how long is your day (you app position Lat Lon).

Modern cells make a fair amount of power on a gray day.

sparrow2 wrote:

I guess this is to avoid a noisy generator! (And a cheap 2 stroke generator could probably be the backup for when it rain).

** It's interesting to note that grid-scale renewable energy (solar, wind) production will continue to need reliable (coal, gas, nuclear) baseload generation on standby until a new generation of battery (or other) technology is developed to provide acceptable cost and storage density

You are correct, but you forget hydroelectricity, whey hold back the water when we don't need the power.

And we also have a lot of small power plants that run on wood, that make local heat, but also electricity

There's not a great deal of hydro in the UK (c. 2%), although the Dinorwig project is well known. It pumps water up to the top of the 'mountain' when electricity is cheap and abundant, then lets it run back down through the turbines to cover peaks in demand. It's limited by the storage capacity of the reservoir, about 9 GWh.

Locations with lots of solar potential tend to be flat and have little water, e.g. deserts.

We don't have hydro here either, buy from Norway (and Sweden), at the moment we buy 1.1 GW from Norway and most of that is hydro. When the wind pick up we will send more than 1GW the other way.

And on the solar side we make more than 0.6GW with solar at the moment.

sparrow2 wrote:
And on the solar side we make more than 0.6GW with solar at the moment.
similar here

COP HSL for Current Day Forecasted and Actual PVGR Power Production

via Current System Conditions (Electric Reliability Council of Texas)

Glossary - A (ERCOT)

"Dare to be naïve." - Buckminster Fuller

If we say 3 KWH a day, with sunshine about 5 hours (and cloudy and other 3-5 hours) , will need about 500 W so 2*250W panels, but better with about 3 panels.

if you live a very hot place you will gain 10-20% if you actively cool the panels.

The amount of batteries really depends of your Iron use when it's dark.

If you use cheap car batteries you should only discharge with about 1/3 of the capacity. So a normal 12V 60Ah will then only hold you about 1/10 of your energi.

(perhaps a used lorry battery (24V) would be the best for the money).

Again which voltage do your Iron use ? and what would it say to getting DC ? and if it get less voltage (-20%) I assume it still will work the on time will just be bigger.

The panels I have is about 30V 8A, so perhaps 4 panels could run the Iron

Discharging 1kW from a 12V battery means 80 amps of current. That's a similar rate to starting a car engine on a cold day, and that usually only lasts for a few seconds.

Methinks the most expensive part will be the fat copper cables and all the necessary safety features, and the professional advice to install it all safely !

I have a 100W panel at our off-grid allotment but that's just for lighting, water pump and trickle charging power tools. My 100Ah battery would take 20 hours to recharge at 5A. My other half blagged the battery for free from the local recycling centre.

The challenge with battery charging is that most common panels output around 21V. A simple PWM controller 'wastes' 30% of that when charging a 12V battery at 14.4V. I am working on a board that uses a switching regulator circuit to capture more of the solar energy, hopefully nearer 95% efficiency. That's straightforward at 5A (75W) but I personally wouldn't feel confident going any higher than that. AVR based, of course ;)

1. How many watts solar panel do we need for house ?

2. How many PVI battery do we need ?

3. How many watts inverter do we need

If you are asking these basic types of questions, it seems like you need to consult with a solar installer--it is in your interested to have it planned properly!

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

avrcandies wrote:
eems like you need to consult with a solar installer

Seems like he needs to listen in class to answer his homework questions himself.

andrewm1973 wrote:

avrcandies wrote:
eems like you need to consult with a solar installer

Seems like he needs to listen in class to answer his homework questions himself.

I which case he'll either get an A* or his teacher will smell a rat. That's assuming he hasn't burned his house down trying to draw 80A down a piece of bell wire.

trying to draw 80A down a piece of bell wire.

Why that's the charge indicator...the more it glows, the longer you are good to go.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Hello ansh11

Lets summarize some of the important things above and add a few more details:

1. The amp-hours (that is NOT amp/hrs, two very different things) coming into your system from the  solar panels must be no smaller than the amp-hours used. If you do not have enough amp-hours coming in, you will use up all the electrical energy before the end of the day.

2. amp-hours in depend on a lot of things, including:

a. ampere rating of the panels

b. the angle of the panels with respect to the sun path. This varies during the day and from summer to winter.

c. weather, especially clouds

d. length of the day

e. shadows that fall on the panels during the day

3. The ampere-hours that you CAN get is really hard to estimate.

4. The usual strategy is to store energy. And, you store quite a bit more than is used in an average day when the sunlight is "average". This typically means storing several days worth of energy (amp-hours). Using this strategy, you will continue to operate with several poor days in a row. The problem is that this raises your cost.

5. Another strategy is to make the panels large enough to generate several days of stored energy in 1 ordinary day. This will insure that the stored energy will be recharged adequately after several poor days in a row.

As you may guess by now, this is NOT easily determined. It really is best to seek the help of someone near you (similar weather, similar sun patterns, and such). Listen to what has worked for them and what has not. THEN, choose your components to fit your circumstances.

Good luck

This is a Good Thing to do!

Jim

Until Black Lives Matter, we do not have "All Lives Matter"!

Last Edited: Sun. Jul 26, 2020 - 06:00 AM

Interestingly, due to the proliferation of solar systems, there is a lot of hard data to draw from. The solar companies have this, so they can estimate fairly accurately what yield can be expected.

This information may be harder to get in other countries (e.g. India).

Jim

Until Black Lives Matter, we do not have "All Lives Matter"!

Last Edited: Sun. Jul 26, 2020 - 06:03 AM

ka7ehk wrote:

This information may be harder to get in other countries (e.g. India).

Jim

I contacted some sellers and asked for more information, I got a one email, they share following information

Components

1. Inverter - 1800 VA (1 no.)
2. Battery -  150 Ah (2 nos.)
3. Solar Panels - 1125 Watt, 24 volts (375 watts * 3 nos.)

Kartman wrote:
Interestingly, due to the proliferation of solar systems, there is a lot of hard data to draw from. The solar companies have this, so they can estimate fairly accurately what yield can be expected.

I've never tried to build a power system in orbit around Tau Ceti, and somehow I don't think they have either.    S.

ka7ehk wrote:

4. The usual strategy is to store energy. And, you store quite a bit more than is used in an average day when the sunlight is "average". This typically means storing several days worth of energy (amp-hours). Using this strategy, you will continue to operate with several poor days in a row. The problem is that this raises your cost.

5. Another strategy is to make the panels large enough to generate several days of stored energy in 1 ordinary day. This will insure that the stored energy will be recharged adequately after several poor days in a row.

It's rather like living hand-to-mouth, where what you earn today feeds you tonight, and if you don't work you go hungry. But each additional day's worth of capacity doubles the panels, batteries and costs.

You have to size for the worst day(s) in the worst season, unless you can temporarily increase generation and storage capacity in the winter.

ansh11 wrote:

I contacted some sellers and asked for more information, I got a one email, they share following information

Components

1. Inverter - 1800 VA (1 no.)
2. Battery -  150 Ah (2 nos.)
3. Solar Panels - 1125 Watt, 24 volts (375 watts * 3 nos.)

That doesn't mention the charge controller but maybe that's included with the panels. Or the cabling and installation which, compared to the price of cheap Chinese hardware, will add a significant amount. Copper and skilled people are expensive.

There's a roaring research field in using magnetically-levitated flywheels as energy storage, but I don't really think any are quite ready for prime-time.  A Google search on the subject came up with many promising companies with promising ideas and a few research papers but nothing exactly for a typical house for sale - at least not for a reasonable price.  S.

It's just that distressing tendency of flywheels to pull themselves apart when the rotational speed exceeds the design limits (i.e. you're pumping too much energy into them...)

Neil

p.s. why can't I just have a dustbin sized Mr Fusion generator in the back garden?

There is no worthwhile energy storage system such that, when the energy stored therein is rapidly released, doesn't go boom.  That's sorta the very definition of energy release.  Gas tanks, diesel tanks, battery meltdowns, et cetera.

barnacle wrote:

It's just that distressing tendency of flywheels to pull themselves apart when the rotational speed exceeds the design limits (i.e. you're pumping too much energy into them...)

Neil

p.s. why can't I just have a dustbin sized Mr Fusion generator in the back garden?

That's because in Back To The Future Part IV Biff gets the upper hand again and sees to it that the movie Back To The Future Part IV never gets made.  So there.  ;-P

S.

(In case you care, some think a good idea is two counter-rotating flywheels, such that if the energy keeping them apart is lost, it gets very rapidly turned into heat when they fall onto each other - if not quite as rapidly as a bomb does exactly the same thing.  S.)

My main power load is air conditioning, and it all occurs in July and August after the humidity builds up. That will use nearly as much power as the rest of the year combined. I can swamp cool in May and June, also September, for the cost of running a little fan and pump (basically 20\$ added to the monthly bill). Is it a waste of water? Perhaps but making electricity uses lots of water also because that is how the waste heat is dissipated. If I could figure out a way to swamp cool through summer, then my seasonal load would be a lot more compatible with solar + storage.

my projects: https://github.com/epccs

Debugging is harder than programming - don’t write code you can’t debug! https://www.avrfreaks.net/forum/help-it-doesnt-work

I guess it depends on whether your objective is to save money or be more ecologically friendly. It's possible that the OP's challenge is different again ... no nearby grid.

Economies of scale would suggest that once grid-scale renewables reach a certain point, there's little value (from either perspective) in doing it individually at home. And I do worry about the eco impact of Chinese manufacturing practices for all those PV panels.

Like most eco-friendly things, it's not so much about a few people doing it perfectly, but everybody doing what they can.

When I lived in the middle east I acclimatised to high temps and low humidity. Indoor a/c was always set to 25C. I've never seen anyone with domestic a/c in the UK, and we *heat* our homes to 25C !

There's a roaring research field in using magnetically-levitated flywheels as energy storage, but I don't really think any are quite ready for prime-time.

Remember when each home of the future was going to have its own small nuclear reactor?   Just like buying a refrigerator, you could get the small or deluxe model.  Not sure how much the extended maintenance plan would cost---but surely the salesperson would say---you don't want a nuclear meltdown just before having dinner guests over."  You also weren't allowed to dispose of old units at the curb.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

barnacle wrote:
It's just that distressing tendency of flywheels to pull themselves apart when the rotational speed exceeds the design limits (i.e. you're pumping too much energy into them...)

If you want to store energy to power a car that way you need two wheels next to each other spinning in opposite directions or when you try to turn the car you get that cross product effect and the front end can lift up off the road.

Kind if recall that back in the  1970's, San Francisco had a couple of  flywheel-driven buses.

Jim

Until Black Lives Matter, we do not have "All Lives Matter"!

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Well, F1 cars now have a system like this.

A number of modern cars seem to have it as a result.

Hybrid vehicles sort of have it except they do not charge a flywheel, but put charge back in batteries.

i think the Flintstones had it right, plus it can even out your lawn.

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

getting back to the topic,

ansh11 wrote:
I live in India

Surely, it must be quite common to do this sort of thing where you live?

So there must be local people with real-life practical experience of what works in your particular location.

You would be far better seeking out local advice on this!

Top Tips:

1. How to properly post source code - see: https://www.avrfreaks.net/comment... - also how to properly include images/pictures
2. "Garbage" characters on a serial terminal are (almost?) invariably due to wrong baud rate - see: https://learn.sparkfun.com/tutorials/serial-communication
3. Wrong baud rate is usually due to not running at the speed you thought; check by blinking a LED to see if you get the speed you expected
4. Difference between a crystal, and a crystal oscillatorhttps://www.avrfreaks.net/comment...
5. When your question is resolved, mark the solution: https://www.avrfreaks.net/comment...
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