http://www.treehugger.com/files/2010/07/ask-pablo-generator-or-battery.php

Treehugger's expert (I have no idea who Pablo is) looks at the economy and ecology of generators (gas or diesel) vs. batteries and thinks batteries are the winner despite higher initial costs.

Clearly portability was not an issue in his analysis. :-> The question is what happens as the lack of power drags on. If there's no electricity, there are no pumps for fuel, so which lasts longer - all that year-old gasoline in your cans or batteries in the same kWh ratings as your gennie plus gas?

I know virtually nothing about photovoltics.

Can you use solar panels to charge deep-cycle batteries directly?

I'm not really thinking about a massive array of panels to provide 30-40kw, but more of a way to keep vaccines, insulin or a small amount of food cool.

Sue

I see a 12V SLA battery as a good source of power for laptops, recharging AA batteries, cell phones, etc. Adequate sunshine, a decent solar panel, and a 12V charge controller (to prevent over charging) should keep the 12V battery topped off and in good state of charge. You could power most of your personal use items with no generator. Even if you had a generator, it'd be kind of a waste using it to power/charge small gadgets. A good 12V battery should last a year or maybe two. Save the generator for the AC.

As one that has lived off the grid for over 12 years, I would not recommend using solar as a power source for a fridge that stores insulin. Insulin has very rigid temperature requirements. Even changing the temperature up and down within its normal storage limits can have an effect on it potency.

Fridges, even small ones use quite a bit of power. Remember that they run 7/24. The problem arises when you have a long period without sun. In Maine, we can get WEEKS of dreary rainy weather. There will be some solar charging during that period, but not much. You would need a very large battery reserve to get you through that long period, which may happen very infrequently. But with Meds, you can not take a chance of failure.

Now if you also have access to a generator for that uncommon, but long dreary period, that is another story. Or if you are in Arizona during the sunny season you might get away with reasonably sized system. But again, with meds, you can not take a chance.

You can charge a deep discharge (or almost any other) battery from solar. However there should be some sort of "controller" between the panel and the battery. Without the controller you stand a very good chance of over charging the battery and boiling off the electrolyte, resulting in a failure condition. The controllers are not expensive for a small system using a standard "flooded" (car type) battery.

Nomad.

In areas (lower latitudes) where sunshine is strong all year round, in theory you don't even need a deep-cycle battery to keep a refrigerator or freezer working as the freezer is able to maintain a working temperatures for a few days so that the time constant for the refrigerator/freezer as it gains higher temperatures is much longer than the solar energy cycle time constant. The battery is only there to allow the storage of electrical energy, which allows electrical loads to be higher for shorter time periods by comparison to the lower but longer time period solar energy input. The battery works as a means of regulating a constant supply of electrical energy. A freezer or refrigerator doesn't need a constant supply of electrical energy as long as you keep the door shut. A battery used in conjunction with a good efficient fridge will keep maintain set point temperature much more accurately though.

http://www.mysolarshop.co.uk/solar-fridgefreezer-kit-p-47.html

It is entirely possible to use solar PV to provide a constant source of boiling water without a battery. With a system such as Quooker hot water boiling tap the electrical energy required is only around 300W to raise the temperature of the water to boiling (well within the capacity of most small domestic solar PV installations) but may take a few hours to raise the temperature to above boiling point i.e. 100C. But the Quooker has a vacuum bottle to store the water and then only requires around 10W to maintain the water (about 3 to 11 litres depending on the model) above 100C.


It is also possible to cook using solar PV without a battery using the slow cooker (crockpot method) using a programmable highly efficient induction hot plate such as

http://www.verynice2.com/stellar-touch-control-induction-hob-sea02.php

when used with a cast iron cooking pot which is insulated to reduce heat loss. (even a straw insulated box can be used directly over the hob and the heat is generated by the cast iron cooking pot and not the hob itself.)

Again setting the hot plate to its lower settings i.e. 150 to 300W will allow slow cooking over a 3-4 hr period.

With highly efficient LED lighting it is possible to light a home with less than 200W peak lighting load. But you will need a battery to store the solar energy collected during the day for this because the sun doesn't shine during the night time.

You can do a surprising amount with a 500-1000W solar PV installation together with energy efficient appliances.

In my thinking the question of generator or batteries is a bit nonsensical. Generators have a high minimum fuel use. From running at 40 or 50% capacity down to nothing at all they use the same relative amount of fuel.

On the other hand contemplate the needs. There are large loads that need to be handled regularly but most of the time the need is much more modest. Hardly large enough to justify starting a generator.

A battery bank, charge controller and inverter allow excess capacity, fuel disappearing up the exhaust stack while producing little useful effect, to be captured by the batteries and used later. Once charged the batteries and inverter allow light loads to be handled without having to start the generator or waste fuel on light loads. Doing this gives you more flexibility and increases efficiency.

Edited to correct sloppy and confusing wording.

My brother set up a battery system.
He was using a small wind turbine as well as a solar panel to charge the battery bank.
He still needed a small generator for heavier loads and emergency uses.

You need a controller to prevent overcharging and if you need to boost the battery power up to mains voltage you need an inverter.
He also had to watch his power consumption on the batteries.
Only so many minutes of lighting, so many minutes of radio, etc.

He used wood heat as well as propane for cooking, propane to run his fridge/freezer too, so his electrical loads were lower than what most people would have.

> There are large loads that need to be handled

Yeah, if you're thinking of running your air conditioner to cool your home, batteries aren't going to cut it, unless you have very adequate solar or wind replenishment. Most of us realize when the power goes out, we're not going to be running our house off whatever independent power source we have.

Each option has its benefits and problems. If you're going to be a couple of days at a time without power, batteries may be the better option because you don't have to keep containers of gasoline and rotate the containers in and out to prevent the gas from getting stale. You keep your batteries trickle charged off the main power when it's there. If you'll be a week or more, a generator may be better because gasoline has more energy per pound than batteries and generators may offer more watts than you can get from any practical amount of batteries.

In either case, you need to know what your power consumption is and match your system to your needs, taking into account how long your power outages last.

I live in an area with very mild weather - it's never below freezing, and we don't have an air conditioner. I wouldn't try to run our whole house on a gennie, and in our situation it's practical to use batteries for individual items.

An integrated approach would be useful. A combination of local battery storage, wind turbine, local generator (either LPG or petrol, Diesel or even wood gas) and solar water heating and solar PV. All these approaches are expensive for the initial outlay costs. In a cost benefit analysis, one of the most important considerations is reducing the load on the appliances which are available and now deemed absolute necessities for the contemporary lifestyles most demand.

One of the problems when the mains power goes out is not really the imperative or the ability to survive as many problems can be improvised or overcome, the real problem is maintaining the convenience based consumerist lifestyle fought so hard by feminists over the last 40 years to achieve the push button instant ping culture of instant gratification.

Everyone now expects to live with fully fitted carpeting and vacuum cleaners and air conditioning and surround sound cinema HD TV setups and dish washers and microwave ovens and clothes washer and driers and electric irons etc let alone all the work top kitchen gadgets. Most of these high load electric domestic appliances are essentially manual labour saving devices, which were once the domain of physical female labour around the home.

Perhaps we should forget the battery versus gennie argument and have the mangle and clothes line and rug beating stick back on standby. My grandmother never had a problem but then she never really used to watch any television soap either in the days before microwave supermarket instant plastic shrink rapped meals became available. Perhaps thats why eastern Europeans look fitter than their western counterparts.

http://www.ehow.com/how_4962302_beat-rug-clean.html

It all started with the introduction of the teasmaid and pong.

http://www.youtube.com/watch?v=G3PK53b_3qo
http://www.youtube.com/watch?v=9r3GIuCnvqo

I had to look up 'teasmaid', but I do remember Atari's PONG... jeez, that was a long time ago!

Sue