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August 12, 2010 at 8:37 am #36717
Hi everyone,.. 1st post here after a lot of reading, and hoping for your input on my “master plan”.
I’m a married man with 2 young kids, and myself & my wife are planning our first off grid venture. If all goes to plan we will have a derelict cottage on an acre site this time next year and will be extending & renovating it to make a completely off grid family home.
My budget for this isn’t massive,.. but I figure that anything I spend on off grid technology will pay for itself eventually. I’m hoping to use technologies that will pay for themselves within 5 – 7 years where possible.
But here’s the thing,… While I want to go off grid, I don’t want to give up any of my modern conveniences. TV, washing machine, dishwasher, microwave etc will definitely be staying,.. so I’m looking into some rather large systems, and this is where I need advice.
The site is fairly windy & situated near the top of a hill overlooking a valley,.. my initial research suggests that a 3kw wind turbine supplemented by a mid sized PV array should provide enough power to suit my needs once I go for A rated appliances & low energy light bulbs etc. Does this sound about right to you guys?
Once the problem of generation is sorted,.. the next hurdle is storage. I have seen on ebay some HUGE 2v industrial batteries lead/acid (from a submarine apparently!)that I could us to make a battery bank. Figuring I’d need a week’s backup supply in case of no wind,.. what size & design of battery bank would be best?
The final hurdle is converting all that DC into usable standard voltage AC. What kind of hardware would I need to run an entire house? I would like to have near the same basic specs as a grid tied home, which I think as standard is a 32 amp supply,.. is it possible to get close to that or am I just dreaming?
My heating system will be mostly solar, using an massively oversized panel system to heat a highly insulated indoor pool. The pool water’s energy will be used via a heat exchanger to run the underfloor heating,.. but a heat pump will be installed because solar alone may not be enough in the winter months in Ireland regardless of how oversized the system is,.. however there are normally plenty of winter gales to power the heat pump!
Any idea’s/info/criticism (constructive!) is appreciated.
NathanaelAugust 12, 2010 at 4:57 pm #40919
Think propane for cloths dryer and cooking stove,
When you use a dishwasher if you wait until it’s full which is
energy efficent it really just a place to store dirty dishes
and if you do them after every meal you use to much hydro
Had one when the kids were small and when it broke after
12 years I refused to replace it and now even my wife
admits the house stays cleaner. Most systems have battery
storage for 3 days windmill with a solar panel or 2
1kwhr generation wind and 1kw solar is pretty standard
3kw/hr * 24hrs * 30 days = 2160kw Check your hydro bill
and yes thats only if the wind blows 100%August 12, 2010 at 6:20 pm #40920
I design systems like you are contemplating. However there are some glaring inconsistencies in your description that could cause you a lot of expense and grief.
“the site is fairly windy” is a very subjective observation as in how much is ‘fairly” windy. You need to know exact speeds and duration of wind. Might I suggest two smaller wind turbines instead of one big one. Every wind turbine has a minimum start speed and bigger units have a higher start speed than smaller ones. This way you are more likelty to generate power in light winds that would not be sufficient to turn the big model.
You did not say where you are located. Latitude and amount of insolation in terms of annual hours of usable sunlight is critical. Solar is the most expensive method and if you indeed have lots of wind this could be a lot more cost effective.
Be careful of used batteries. If they are free then you only incur the cost of hauling around a lot of hazardous material but these batteries wer taken out of service for a reason. Why? You need to determine the internal condition of these usd batteries before you expend time, money, and effort to set them up.
Many people do not understand this but you can have too much battery bank for a given system. I have been salvaging batteries and designing systems for a decade now so I have a little bit of experience with it.
Your comment that you think a 32 A supply for a grid tied home is about average makes me wonder where in the world you are located. Is this a 230V 50Hz country? Your question makes me wonder how much product research you have done. Yes it is possible to do all these things and the hardware is available off the shelf. In fact my wife’s uncle lives off the grid and has all the things you want. Begin by looking into Victron products. Also look at their section advertising installations of resorts in Africa among other places. Look at the battery houses needed to support such an installation. It can be done but it will be expensive.
Using the mass of an indoor swimming pool is fine except you overlook the loss of efficiencies if you plan to use the pool for swimming. The system would work much better if the temperature was hotter but that would render the pool unsuited for swimming unless you like to boil yourself to death. your solar heated water will reach 160F or higher and water than is only 70F – 80F is not going to give you an effecient and comfortable heat transfer for heating the house. The increased size of the radiators needed to work with such low temp medium is going to make them very expensive compared to a system designed properly.August 13, 2010 at 5:21 pm #40922
Batteries at best last 5 years just because you can get them
at low cost this time remember that the system will need
maintenance with battery replacement periodically.August 14, 2010 at 3:14 am #40923
Propane is an excellent choice for off grid but last year I discovered a limitation of Propane. We had an extended period of below 35 degree weather and our pipes froze. I attempted to use a propane fuelled heater then blow hot air under the building. The burner started fine but after a few minutes the flame died. Changing to a new bottle did not help. Eventually I realized it was so cold outside the propane would not vaporize in the tank and this could not build up enough pressure to power the torch. Many places are supplied with a 1500 L propane tank placed outdoors but close to building. For those living in areas subject to cold weather consider providing some form of insulation and a heater source of some kind. For off grid locations this latter could be a real challenge. One possibility is an emergency gasoline generator to power electric heaters located inside the insulated container of the propane tank. Remember it does not have to be a lot of heat. Just enough to bring the tank and content above the vaaporization point by maybe 10 degrees. Enough at least to provide sufficient pressure for whatever appliances are fuelled by the propane.August 14, 2010 at 9:20 pm #40927
Thanks for the input guys.
I am in County Cork in Southern Ireland,.. so long periods of sub zero temps are rare,.. although the effectiveness of PV panels in this hemisphere are limited in the winter I know. We have a 220V 50hz supply from the grid here.
The idea of multiple smaller wind turbines instead of 1 big one is interesting & something I hadn’t previously considered. Is it hard to combine multiple generating sources to charge a single battery bank? It certainly would be cheaper to have three 1kw turbines than one 3kw one.
I have conceded that propane will be required for cooking,.. but in Ireland propane powered clothes dryers are unheard of,.. and the cost of importing would probably exceed the cost of making the system bigger to cope with the extra load.
As for the swimming pool,.. I should elaborate. There will also be a high temp tank for the house hot water supply as in standard systems,.. the swimming pool heat will be used to run underfloor heating or those special low temp radiators (They look like a car radiator inside with a mesh of metal fins & a small fan to aid convection). Even with heating that works using lower temp water, the pool temp will be slightly too low (or the pool uncomfortably hot!) so it would be supplemented either from the high temp tank, heat pump or (new idea) a waste oil burner.
The control systems for this would be complex I know, but far from impossible.
Also the comment on over-sizing battery bank being a bad thing,.. I understand this is because leisure battery’s need to be discharged below 50% regularly (once every 2 weeks was mentioned to me) and then re-charged fully regularly to maintain them and maximise their life? To overcome this issue I had considered splitting the battery bank in 2, setting up a voltage sensor & timer so that on one day a week 1 bank is automatically disconnected (once the bank isn’t already below a set limit) & discharged for a set time period (a pool heater/immersion heater etc would be a good use for this energy) while the other bank would still be sufficient to run the house. The next week the other bank would automatically disconnect & discharge.
Is this a practical solution?
Whilst understanding that over-sizing the battery bank could be seen as silly,.. I will have NO grid access and running a generator with Irish fuel prices would be madness.August 15, 2010 at 4:46 am #40931
Cost and avalibility is everthing most systems keep the
batteries on a float charge, atomatic switching is avalible
look at the cost and specs of a marine deep cycle battery as
to a off gridAugust 15, 2010 at 6:19 am #40932
@njones to answer your question regarding multiple charging sources. This works well when the charging sources are in bulk mode. If you also incorporate the idea of splitting the bank then it definitely will work right up to float stage. Most of my system designs incorporate dual sources for charging. In off shore yachts any failure is far more serious than on land.
If you are considering keeping livestock give some thought to a methane digester. The resultant biogas ( methane ) will serve as fuel for a genset. If you google Methane digesters you are sure to find several examples. One of the most impressive You Tube videos I saw was of a German built generator of approximately 250 kW but there are also a number of examples of single cylinder under 10 HP generators suitable for charging a home power plant. Getting back to hot water heating. I work with a company that deals with wood burning boilers and radiant hot water or radiator heating. If the water is below 110F it has too little differential to be effective with a radiator. Our systems are open circuit meaning the resevoir has no pressure cap and thus cannot build up pressure. It also cannot reach higher than boiling temp but normally the temp is in the range of 110F – 135F or thereabouts
If you do not have sufficient differential between hot water and room temperature you do not get a fast enough heat transfer through the radiator. In order to transfer enough BTU per minute or per hour you end up needing larger radiators and you probably already know what that will cost. Higher water temp means you can use smaller radiator to shift an equal amount of BTU.August 15, 2010 at 8:52 am #40933
I will look into the methane generators,.. it could be a perfect solution!
Would the underfloor heating not be enough to allow a low temp system to work? Using the entire floor space as one giant radiator?August 15, 2010 at 12:25 pm #40934
Another question,… I was just reading through some old threads about psw inverters. The thread mentioned using multiple smaller inverters instead of one big one,… which would be obviously a lot cheaper & add a measure of reliability (if 1 inverter fails I assume the remaining ones would still provide power?).
1. Hard to implement?
I can get 3kw inverters for a fairly reasonable price,.. I assume 6 of them joined together would provide more power than I would ever use even at peak consumption with washing machine/dishwasher/lights/tv/microwave etc etc all running at once?.August 15, 2010 at 9:00 pm #40935
Have you done a power budget? 6X 3kW gives you a steady 18 kw (surges to 36 kW) which is an awful lot of power. My wife’s uncle lives off grid and has all the amenities including big screen TV surround sound and a jacuzzi in the ensuite bathroom for the master bedroom. His wife has every sort of kitchen appliance in the enormeous kitchen. Their daughter and husband lived there with a new born infant (and attendant laundry) until their own house was built. This was all powered by a 3 kw Outback inverter. Only the 350 foot deep well pump required a boost when pumping. Measured peak surge was 7.5 kW which is just a tad more than the inverter sould surge to.
Yes multiple sine wave inverter make sense in some instances.
Getting back to methane powered generators. Thereis a hobby group which included members from the UK whose interest focus is the venerable old Lister engine and Indian built Kisteroid clones as well. One person in Victoria BC heated and powered his entier home over the winter with the waste heat from the engine coolant system and electrical power from the generator driven from the motor. The concept is called micro co generation. The website is http://www.microcogen.com Victoria’s climate is similar to county cork in Ireland. You would likely have similar heat and power needs.
In a nutshell the coolant is circulated through radiators or radiant floor heating pipes. Some of those hobbyists even build their own exhaust stack heat exchanges. There is at least one dealer in the UK who can supply turn key installations should you prefer this approach.August 16, 2010 at 3:54 pm #40937
My thinking on the 18kw is that this is a good safety margin above my absolute maximum,.. it will never be reached hopefully! My thought was in the mornings,.. washing machine going (2kw), microwave on, tv on, lights on, kettle (3.3kw on its own), toaster on, the hoover going, etc etc. There are circumstances in my home where for short periods I could use near that much power. Prob for only 3 or 4 minutes,.. but I don’t want to wait for the kettle to finish before I put on the toaster etc etc. If this is going to work for me it has to do EVERYTHING that the grid does.
I want my house to be like a “normal” house,.. I don’t want to have to think before i switch something on,.. I’m happy to pay extra to begin with so it all just works when needed.
That said, the kettle being the most power hungry of appliances will be replaced with one of those low power hot taps that gives instant boiling water but only heats what you need. These are supposed to use 80% less power in the long run, though the draw is still over 1.6kw whilst the water is running.August 16, 2010 at 4:41 pm #40939
Was given a counter top water dispenser with hot/cold feature
hot is 1150 watts. It has totally replaced our kettle, you
have hot water 2-3 minutes 2 – 2-1/2 cups at a push of a
button ours is a polar pwd2635w-2August 16, 2010 at 11:32 pm #40940
NJones you sound just like the self centered people who have got us into this mess in the first place. you want it ALL and you want it RIGHT NOW!
Sorry but you just lost any sympathy I might have had. Not only that but your want list displays your lack of technical understanding of how things really work. Doing whay you propose is technically unsound and totally wasteful
You had better stay on the grid.August 17, 2010 at 6:55 am #40942
Why do you think renewable technology is slow to catch on? Why do you think many of the pioneers of these systems are considered “tree hugging, sandal wearing hippies” by the general public en-mass?
Its because the majority of existing systems are minimalist,.. you cant have the modern conveniences that the world today is addicted to, therefore it will NEVER catch on in its current form.
I want my house to be a show piece,.. I want to be able to show the world that renewable energy can run all their modern conveniences, & with the right control systems can do so reliably, automatically and with an absolute minimum of maintenance. It CAN be just like a “normal” house, but without damaging the environment,.. and its easy to do and (in the long run) cheaper too!
My lack of technical knowledge on the subject is why I am here. I have the engineering ability,.. I’ve built houses before, installed rainwater harvesting, drinking water purification and small diy solar hot water rigs etc etc. I want to add to my knowledge & scale up everything I’ve done before. I just need some info & wiring diagrams,… I’ve a year before construction begins so now is the time to learn.
You say “technically unsound”,.. tell me why it is, & tell me how to fix it whilst retaining the features I need? You say its “wasteful”,… I agree, but I’ll be wasting zero carbon renewable energy that will be raining down on us in plentiful supply for a few billion years to come,.. I can live with that.
As for wanting it all & wanting it right now,.. I’m married with kids,.. saying “sorry hun, you can’t put the washing machine on until this other appliance has finished” will get me only grief & a divorce. Personally I’d live happily in a shed (once there was internet connection!).
I believe that systems like the one I want will be common place in 10 -15 years,.. everyone will want one, and with oil nearly gone, everyone will need one.
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