Saturday, November 19, 2011
Free Renewable Energy Not Always So Free
Being eco-friendly may be admirable, but it comes with a price, and it is not always as crystal-clear as one believes.
We rely heavily on non-grid energy, including wind and solar power. However, renewal energy sources such as ours require energy storage, and, specifically, battery storage. While there are advanced battery technologies on the market (e.g. batteries for hybrid vehicles), as well as large wet-cell storage batteries (such as those in forklifts and indoor industrial cleaning equipment), the most prevalent, and therefore, the lowest-priced units are conventional deep-cycle marine 12-volt batteries. These typically cost from $80 to $200, with only modest storage and cranking amperage.
The primary advantage of marine batteries over vehicle batteries is their capacity to be discharged to low levels and recharged often. However, “often” is subjective, with most of the commercially available units being rated for a few hundred charging cycles, at most. These batteries also do not like to be frozen, but really detest excessive heat.
In order to supply minimal energy, such as the energy to light two compact fluorescent bulbs four hours each day and a small bar refrigerator (drawing 90 watts, with a surge of 800 watts), you will consume 2,280 (2.3 kw) watts each day. Now consider that a small solar panel produces 13-18 watts (some of the single panel retail units produce 30w) under optimal conditions. In northern latitudes, hours of summer daylight average 15 hours, but typically generate only about 60% of that in sunlight sufficient to “max out” the solar panel. With three panels, you will produce 405 watts – less than 20% of what you need. A small wind turbine may produce 40% of what you need, if you live in an environment where the wind is very frequent, and of sufficient strength to power the turbine. Typically, the marine batteries attached to your collectors are rated for 800-1000 CCA. Obviously, unless you expand your generation and/or storage network, you will need to use a charging system on the batteries.
Because each of the batteries is being discharged the equivalent of 100%every eight hours, you will require a battery array of at least three batteries, just to produce your daily minimum energy requirement. Ultimately, most of us will require electricity for television or sound equipment, charging cell phones and laptops, power for small fans, and so on. With minimal energy, though, your three-battery array will be fully discharged and recharged 100 times from June to September. That is the normal lifespan of the battery!
This year, we experienced near-record heat and sunlight throughout our summer. While that is great for our solar panels, heat is more damaging to the batteries than cold, and reduces their ability to be recharged (and hold a charge) significantly.
We used an eight-battery package. However, almost weekly, we needed to refill the cells, as the electrolytic acid evaporated. The sunlight did its damage, too, destroying one battery. Of the eight, only one battery now holds a significant charge, even though I de-sulphated the batteries regularly. Five of the batteries were three years old or less, with the other three being four years old. Seven batteries will need to be replaced.
At a cost of $90 per battery, our outlay will be $630, plus taxes. We used nearly $100 of generator fuel to supplement our renewable energy supply. In four months, our lighting costs will be $700-800, factoring in the wear and tear on equipment.
Now, we have batteries that need to be recycled and spent fuel that polluted the air. If we had relied on our hydro-electric grid for energy, at a cost of $0.08 per kwh, we would have spent less than $130! Did we really do the environment and our pocketbook a favour?