Some basic energy Qs

Afternoon All,

Just found this great forum, so this is my first post. I'm pretty new to permaculture so currently on a steep learning curve.

I am currently contemplating trying to design and build my own off-grid home and trying to get my head around whether it will be possible to go off-grid with my budget.

I have calculated that my daily energy usage will be approx:

Lighting: 3 40 watt bulbs @ say 3 hrs average per day = 360 watts per day

laptop: approx 65 watts*5hrs=325 watts

Projector for watching movies via laptop: approx 200*2hrs=400 watts

mini Fridge: 100 watts * 24 hours = 2400 watts per day.

So total daily estimated energy requirements = approx 3.5 KW per day. So bearing in mind that I'm totally new to all this (patience please!) my questions now are...

- Does the above seem reasonable?
- What would be the best way to practically achieve this with a linited budget. I mean can you really build your own solar or wind power generators (it is a windy site) which will provide this amount of electricity per year.
- I was also thinking of getting a petrol gnenerator as a backup. How much electrcity do these things produce?
-What about human powered generators (I'm a keen cyclist )
- This might seem like a silly Q, but for those of you living off grid, how does it work in a practical sense. I mean is your house wired as normal and then connected to a large battery (if so what size) and alternator which your electricity generating equipment is used to send the produced energy to for storage?

Sortry for so many Qs, but my head is spinning!

Thanks everyone

First things first.  You are going to get yourself mega-confused if you start measuring energy requirements in watts.  You are doing the arithmetic correctly, multiplying watts by hours, but what you end up with is watt-hours.  So 120 watts x 3 hours = 360 watt-hours.  Your total energy requirement, by your calculation, is 3500 watt-hours, or 3.5 kWh.  Watts indicate the speed of energy use, watt-hours indicate the quantity of energy used.

You probably want to think more about your energy priorities.  Do you really need a projector?  And are you really going to use it every day?  Get a laptop with a decent screen and watch the movies on it!

Can you do without the fridge?  What about a root cellar instead?  Will you be hauling water by hand or are you going to want to pump water for household use?

What about seasonal needs?  You will need less light in summer, more in winter.  You won't need the fridge at all in winter, fortunately.

And, speaking of seasonal variations, your electrical sources will vary seasonally.  You will need to acquire statistics for the location you are interested in.  How much sunlight is there in winter for solar?  Wind is often stronger in winter, so a solar-wind combination often makes sense.  On the other hand, wind power is very location-dependent - it won't work well in a forest.

A generator is a practical backup (at least until oil runs out - on a limited budget, will you be able to afford fuel at $20 per litre?).  You can get them in any capacity you want.  Decide how many watts you want, and then figure out how to pay for it.

An olympic cyclist can crank out energy at about 250 watts in short bursts.  An amateur in good shape can maybe expect to produce 100 watts.  So, to produce 3500 wh per day, you would have to pedal flat-out for 35 hours per day!  Nope, that's not going to work.

Since the sun doesn't shine all day (especially not when you want to use lights) and the wind doesn't blow all the time (and you can't cycle all day either), you are going to have to have batteries and a charge controller.

You can't use normal wiring unless you also run an inverter.  Normal wiring is for 120 volts (American) or 240 volts (European) alternating current (AC).  An inverter will give you that by converting the direct current from the batteries, but it costs you some energy to do that.  The advantage of an AC system is that you can use standard appliances.

Or, you can run everything directly off the battery, but then your wiring won't be standard and you can't use standard appliances.  If your batteries are 12 volts, you can find a lot of appliances designed for RVs.  However, most off-grid systems I have seen use batteries of different voltages, which makes finding appliances harder.  Because battery voltage is lower than AC voltage, appliances use more current for the same power, which requires heavier gauge wiring.

Some off-grid folks I know use solar only in an inverter-based system.  They use it to run a light or two, a laptop, charge their cell phone, and charge their electric bike.  They haul water by hand and have no fridge.  Others use a lot more solar panels and a wind turbine to run a full household including electric washing machine (though I think the heat source is propane)

Lots of research to do...

Hi Hobbit,

Loads and loads of questions and there are loads of different answers to them but how exciting - no wonder your head's spinning!   

Anything's possible if you have enough money but if you're on a budget then you may have to take one step at a time and a have the capacity to add to your system as you find a bit more money.

Where is the site where you want to build your house ? Can you find out about the wind and solar potential there, then folk on the forum who know about these things can help to answer your questions better.

We've been off-grid for about 18 years and I've tried to record and photograph all the different processes and steps that we've taken over the years so that I can help other people to do the same thing. I'll do my best to help if I can.

Once you've worked out what sort of renewable energy you have access to, then I and (I hope) other people can help you design a system which will mean you'll never need to pay another electricity bill. 

Edited to say, Hi KeithBC ! - you type faster than me !!

Hi, Hobbit!  just some comments:

1. I would recommend going with the inverter to get standard AC.  Not only does the DC require larger wiring, but you'll experience more energy losses from having to use the larger wiring.  The longer the wire, the greater the losses will be.  Rather than figuring out all of the losses, just go with the AC.

2. Investigate using a chest freezer as your fridge.  Much more efficient, but it takes up more floor space.  Check out How to convert a chest freezer to a fridge  Using this system, the author went from a fridge that used 100 W/hr to one that used 10 W/hr -- one-tenth the amount of electricity.

KeithBC wrote:
First things first.  You are going to get yourself mega-confused if you start measuring energy requirements in watts.  You are doing the arithmetic correctly, multiplying watts by hours, but what you end up with is watt-hours.  So 120 watts x 3 hours = 360 watt-hours.  Your total energy requirement, by your calculation, is 3500 watt-hours, or 3.5 kWh.  Watts indicate the speed of energy use, watt-hours indicate the quantity of energy used.

Ahh yes, with you now, thanks ops:

You probably want to think more about your energy priorities.  Do you really need a projector?  And are you really going to use it every day?  Get a laptop with a decent screen and watch the movies on it!

Can you do without the fridge?  What about a root cellar instead?  Will you be hauling water by hand or are you going to want to pump water for household use?

What about seasonal needs?  You will need less light in summer, more in winter.  You won't need the fridge at all in winter, fortunately.

Yeap you are dead right, priorities is the name of the game. Great idea re the root cellar, thanks. If I can get that to work it'll be a great saving. I'm in Ireland and I've read a few UK posters who seem to have done something similar (http://www.simondale.net/house/forum/viewtopic.php?f=3&t=83), so fingers crossed this will be a viable option. I'm thinking now I can do with on average approx 1KWHr per day

And, speaking of seasonal variations, your electrical sources will vary seasonally.  You will need to acquire statistics for the location you are interested in.  How much sunlight is there in winter for solar?  Wind is often stronger in winter, so a solar-wind combination often makes sense.  On the other hand, wind power is very location-dependent - it won't work well in a forest.

Thanks. In Ireland sunlight is limited although can still provide some energy. The location is on a hill so lots of wind although I think planning permission is needed here.

A generator is a practical backup (at least until oil runs out - on a limited budget, will you be able to afford fuel at $20 per litre?).  You can get them in any capacity you want.  Decide how many watts you want, and then figure out how to pay for it.

Thanks. Do you know roughly how many litres of fuel it would take approx to produce 1KWHr?

An olympic cyclist can crank out energy at about 250 watts in short bursts.  An amateur in good shape can maybe expect to produce 100 watts.  So, to produce 3500 wh per day, you would have to pedal flat-out for 35 hours per day!  Nope, that's not going to work.

Since the sun doesn't shine all day (especially not when you want to use lights) and the wind doesn't blow all the time (and you can't cycle all day either), you are going to have to have batteries and a charge controller.

You can't use normal wiring unless you also run an inverter.  Normal wiring is for 120 volts (American) or 240 volts (European) alternating current (AC).  An inverter will give you that by converting the direct current from the batteries, but it costs you some energy to do that.  The advantage of an AC system is that you can use standard appliances.

I think I'd prefer to go with the inverter option. Is an inverter expensive? Also how much energy do you use converting to AC?

Or, you can run everything directly off the battery, but then your wiring won't be standard and you can't use standard appliances.  If your batteries are 12 volts, you can find a lot of appliances designed for RVs.  However, most off-grid systems I have seen use batteries of different voltages, which makes finding appliances harder.  Because battery voltage is lower than AC voltage, appliances use more current for the same power, which requires heavier gauge wiring.

Some off-grid folks I know use solar only in an inverter-based system.  They use it to run a light or two, a laptop, charge their cell phone, and charge their electric bike.  They haul water by hand and have no fridge.  Others use a lot more solar panels and a wind turbine to run a full household including electric washing machine (though I think the heat source is propane)

Lots of research to do...

Thanks once again for all your great help. Looks like I came to the right place

Irene Kightley wrote:
Hi Hobbit,

Loads and loads of questions and there are loads of different answers to them but how exciting - no wonder your head's spinning!   

Anything's possible if you have enough money but if you're on a budget then you may have to take one step at a time and a have the capacity to add to your system as you find a bit more money.

Where is the site where you want to build your house ? Can you find out about the wind and solar potential there, then folk on the forum who know about these things can help to answer your questions better.

We've been off-grid for about 18 years and I've tried to record and photograph all the different processes and steps that we've taken over the years so that I can help other people to do the same thing. I'll do my best to help if I can.

Once you've worked out what sort of renewable energy you have access to, then I and (I hope) other people can help you design a system which will mean you'll never need to pay another electricity bill. 

Edited to say, Hi KeithBC ! - you type faster than me !!

Hi Irene. Thanks for the reply. I'm in Ireland, so sunlight is limited, but still viable for some energy production. We have good wind potential here (best in Europe I think) and the site is on top of a hill so definitely great wind potential. Any idea of approx money I would need to spend to be able to produce 1KWHr of energy/day on average. Willing to have a go at building things myself if you think this option is viable/worthwhile.

Would be great to hear your experiences. Sounds exactly like what I'm after! Thank you again

Muzhik wrote:
Hi, Hobbit!  just some comments:

1. I would recommend going with the inverter to get standard AC.  Not only does the DC require larger wiring, but you'll experience more energy losses from having to use the larger wiring.  The longer the wire, the greater the losses will be.  Rather than figuring out all of the losses, just go with the AC.

2. Investigate using a chest freezer as your fridge.  Much more efficient, but it takes up more floor space.  Check out How to convert a chest freezer to a fridge  Using this system, the author went from a fridge that used 100 W/hr to one that used 10 W/hr -- one-tenth the amount of electricity.

Hi Muzhik,

Thanks for the reply. I think you are right I'll go for the inverter option. Hopefully they aren't too expensive and hopefully they don't take too much energy to convert.

f I understand right then I need to wire everything to connect to a number of batteries which can be used to store energy created from the various energy producing appliances I decide to use (solar/wind/human generated/fuel generator). Is this right?

Thanks for the chest freezer idea. I'm going to investigate the root cellar idea. Fingers crossed on that one.

Don't worry about all the technical stuff at the moment, this is the sort of thing you should be looking at.

How to find the wind speed in your area of Ireland (If you're in the UK )

http://www.bwea.com/noabl/index.html

Wind speeds today

http://www.accuweather.com/ukie/maps.asp?partner=accuweather&type=wsp

Average wind speeds

http://www.irishsilicon.com/2009/08/average-wind-speed-in-ireland.html

Wind energy is much cheaper than solar, so if you have a windy site you could have mainly wind power with a bit of solar for when there's no wind. You'll need to protect your house to keep it comfortable though. 

Once you work out the amount of energy you can generate, you can decide how you'll distribute it around your house and what you'll do with it.

Hobbit wrote:
If I understand right then I need to wire everything to connect to a number of batteries which can be used to store energy created from the various energy producing appliances I decide to use (solar/wind/human generated/fuel generator). Is this right?

You would wire all your energy-producing sources (wind, solar, steam, poteen) to charge a set of batteries, which are then connected to an inverter.  Here in the states, with 120V AC, most of the people I've read about connect their 12V batteries in series into 48V packs, then connect these 48V packs in parallel to a 48V inverter that will produce 120V AC.  You'll have to see how most people who use 240V systems do it.

You might also be interested in checking out VAWT (Vertical Axis Wind Turbine) technology.  There have been some advances in the past few years that enable VAWT systems to produce more power than previously.  With a VAWT system you may not need to have a tall tower and so need not worry about getting permission from your local planning commission.

The good news is that Ireland is very liberal in the regulations for domestic turbines and you don't usually have to have permission for masts under 13m high - so thats one less thing to worry about ! 

Thanks for the further info guys. I wasn't able to find specific wind info for my site from the links, but based on Irish general wind stats and the fact its near the top of a hill with good winds do you think I would be able to build my own turbine to produce 1KWH per day? Any idea what approx cost we would be looking at?

Thanks again

If you're capable then you can build a windgenerator yourself - there are a lot of plans and ideas on the 'net. For example : http://www.instructables.com/id/DIY-1000-watt-wind-turbine/

We have three wind generators but I didn't build them, so I'll have to leave the technical information about how to do that to someone else. 

Irene Kightley wrote:
If you're capable then you can build a windgenerator yourself - there are a lot of plans and ideas on the 'net. For example : http://www.instructables.com/id/DIY-1000-watt-wind-turbine/

We have three wind generators but I didn't build them, so I'll have to leave the technical information about how to do that to someone else. 

I have neighbours who built their own wind turbine from this (or a very similar) design.  It works well for them.

hobbit this is a great steaming tv channel with lots of info on getting off grid cheap


http://www.americanrenewableenergy.org/

It has already been said, but I'd like to emphasize that the first thing you should do is make an honest estimate of how much electrical energy is needed. This is the basic list; the needs, not the wants. There are many online calculators available for estimating and sizing a system. I have issues with many of them, so I wrote a spreadsheet to estimate loads and factor in things like hours of good sunlight, battery storage capacity and come up with a solution that recommends battery and PV module requirements. It is oriented towards solar, but wind generator inputs could be factored in.

If you or anyone is interested you can download a copy for free from...
http://countryplans.com/smf/index.php?topic=8192.0
Scroll down to the second message to locate the download link.

The same forum has a board topic on off grid power.
http://countryplans.com/smf/index.php?topic=6059.0
We're mainly US and Canadian folks but the off grid basics are the same pretty much anywhere. For example, Outback Power, makers of some of the more reliable equipment, makes inverters for all power markets.

As for a system that uses DC directly vs a system that uses AC power from an inverter, unless the system is very small I believe a direct DC system should not be chosen. There simply isn't much in the way of choices when it comes to devices that require low voltage DC power. With an inverter based system you can use any normal household device. Of course that ups the likelihood of wanting more power.

Paul, I trust you don't mind the links.
MD

Thanks for all the replies guys. Really appreciate it.

Irene Kightley wrote:
If you're capable then you can build a windgenerator yourself - there are a lot of plans and ideas on the 'net. For example : http://www.instructables.com/id/DIY-1000-watt-wind-turbine/

We have three wind generators but I didn't build them, so I'll have to leave the technical information about how to do that to someone else. 

Hi There,

I have found another pretty good resource if you want to learn how to build your own wind turbine or generator. Here it is: http://www.greenenergyhelps.com/how-to-build-wind-turbine/.

The post describes the things that you should look out for and so on. Therefore I thought it should be quite useful.

Thanks.
George

Hobbit, for DIY wind energy you have perhaps the worlds greatest expert nearby!  Look at Hugh Piggott's homepage

http://www.scoraigwind.com/

I have some of the how to books and they are great.

Another source is

http://www.otherpower.com/

Good luck.

The best energy 'budgeting' and effective analyses would be along the lines of the 2000watt/person/day concept and lookingat the embodied energy (which is the ultimate sustainable measurement via LCA -Iso14000series) within stuff.

There's nothing wrong with looking at watts without the hours - it's electrical demand. Utilities like you to convert everything to KWH and $/kwh...which is load.  but if you're off-grid demand is sometimes demand is more pertinent.

I believe that you are looking only at electrical usage... what about hot water, cooking, driving, etc.  The average American uses 11,400.  A recent ecovillage I visited in Germany uses 500KWH/Yr/person!! 

checkout  http://www.buzzfeed.com/jonah/the-2000-watt-society and www.wattzon.com

Fred (EE engineer, unversity teacher)

Chloe Taylor wrote:
Thanks a lot for posting in your suggestions, enjoyed reading them a lot well done....

Thanks! <blush>