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Saturday, September 23 2017 @ 02:23 AM CDT

Alternate Power Sources

Previous: Battery Care and Maintenance - Next: Distant Internet

There are several ways of generating power at remote sites for a live streaming wildliife camera system. The most obvious is solar cells, but don't neglect the option of wind or water generators, and for some situations either a generator or the latest technology in fuel cells may be cost effective. 


Solar Cells

Today’s solar cells are quite a bit better and less expensive than those of as little as 5 years ago, but they are still fairly expensive and take up quite a bit of room. They are also what I’d call an attraction to a site – such that any site with them should consider the possibility of vandalism and theft, although not nearly as much now as in the past.

For a number of years I’ve used a pricing of $10/watt as my basic assumption but it is now down closer to $5/watt for consumer purchased cells of any reasonable size. This means that a 100 watt panel should come in at somewhere near $500 to $600 retail in lots of 1. You can get better prices if you shop around and are willing to take less than perfect cells.

The size of a cell package for a given wattage rating is also coming down as the cells get more efficient. We’re not talking huge differences here, but at least it is happening.

The large panel to the right is rated at 80 watts and is covered with a plastic top rather than the traditional glass. The set of smaller cells in the background is the more traditional crystaline silicon cells - 18 watts per section; 3 sections total 54 watts.

You will need to determine how large a solar array you’ll need based upon the amount of full sun your site will get at the time of the year your system is deployed. Again there are places on the web to get the info for maximum (http://aa.usno.navy.mil/data/docs/RS_OneYear.php ) for a given spot – but you’ll have to temper this with typical weather patterns for that spot. The prairies in Canada get more sunshine on any given day than the West coast of Vancouver Island for example, even if both are at the same latitude.

You’ll also need to decide if your setup will be on during daylight only, or all night too.

Once you have this information you can do a supply power budget and figure out how large an array you’ll need and how large a battery bank you’ll need. The “fudge factor” will be how little the array will generate in Winter with the sun lower on the horizon and shorter days. In our case, for a project close to Vancouver but still where there was less sun on average (about 50 miles from downtown, East in the Fraser valley) the panels provided about 30% of their maximum power, even in full sunlight at noon. Later in the season, the solar panels sometimes produced enough power that the systems ran until midnight before low battery voltage caused problems. If we had had a daylight sensor set to cut off the cameras and radio when the sun went down (we wanted to see if things happened at night, so didn’t cut off at low-light) the solar panels would have kept the cameras going for about 50% of daylight hours except during the period from beginning of December to mid January.

There is the possibility that the array won’t provide enough power, no matter what you do. Long periods of bad weather are the major problem, but simply not being able to hide or mount enough cells is another. In this case you’ll have to decide if you are willing for your project to go off the air, or wish to use some other method of adding or conserving power. See generators and fuel cells as well as automation sections.

Wind Turbine

Small commercial wind turbines with output in the 500-1500 watt range are available. You can also make them with a propeller blade and a car alternator, but the details are left to your ability to search the internet.

The efficiency of a wind turbine is directly related to the size of the blade – the larger the blade, the more efficiently it will turn wind into power – but also the greater the potential for the turbine “running away” unless it has some sort of mechanical brake on it, or has a constant load great enough to keep the turbine’s RPM below its design maximum. This is the job of the charge controller with loading facility.

The charge controller needs to be able to deal with the maximum output of the turbine. The backup battery needs to be able to deal with the likely maximum period of no wind.

http://www.allsmallwindturbines.com/ - list of providers of small turbines

http://www.omafra.gov.on.ca/english/engineer/facts/03-047.htm for basic info

Water Turbine

All that is said of the wind turbine applies to the water turbine. In addition you’ll need to ensure that the device is situated where it can produce a consistent amount of power rather than a maximum. If a flow is likely to diminish over the time the system is in place, it is better to put the turbine where it will always generate power, and compensate some other way for lowered maximum output.

Generator

Generators are almost too much of a good thing. Finding one that puts out small amounts of power over a long term, rather than large amounts for any term, is a problem. A secondary problem is finding a battery charger that can take enough of the output power and deliver it to the battery system such that some sort of efficiency of the total system is possible.

A 1 Kw gasoline or propane generator running at 50% load – a reasonably efficient use of the generator - puts out 500 watts. This is 41 amps at 12 volts. A battery charger capable of sustaining a 40+ amp charge rate for more than a few minutes is worth more than the generator is, much more. A battery bank capable of receiving a 40 amp charge and not over heating and destroying the batteries will similarly cost more than the generator by quite a bit.

In our initial design for the Chehalis camera tower, where we specified 3 cameras and a radio, we were going to use a 1000 amp-hour battery bank of industrial NiCad batteries and a 2 Kw generator for a day about every week or so to charge them. These batteries were to be set up in two banks of 500 amp-hours each, with a battery charger able to deliver about 20 amps continuously (each). The battery chargers cost over $200 each. The generator cost about $600, and the batteries would have cost us well over $20,000 if they had not been used and well taken care of prior to being donated to us.
The generator had an electric start, but there was no automation to start it when the battery voltage fell below any setting. That would be something we had to supply, along with a method of turning the propane (gasoline would not be fitting to have stored on a wildlife estuary) on and off – especially off, since this was the only way of shutting the generator off.

The proposed system included a small single-board computer that itself took something up to 8 watts of power, and that would do some other things (like turning lights on and off, monitoring battery voltages, etc.) but was really there to allow remote management of the generator and charging systems.

A commercial unit of similar capability was priced out at in excess of $5000 without the batteries.

Fuel Cell

After I wrote an article describing our needs for power for the Chehalis estuary project, I was contacted by a representative of the Canadian company importing a German methanol fuel cell. I’ve been watching the whole fuel cell industry, especially since one of the major players is headquartered here in the Vancouver area (Ballard)

The EFOY fuel cell runs on highly refined methanol, and puts out – depending on model – from 600 to 1560 watt hours of power per day at 12 or 24 volts. At the high end, this translates into an output of about 6 amps continuously at 12 volts.

We completely abandoned both the propane generator and the NiCad battery bank in favor of the use of this fuel cell and a 90 amp-hour battery, augmented by 160 watts of solar panels. Even in Winter (this project ran from beginning of November to end of February) we got several days when the fuel cell was only needed at night.

A $200 jug of methanol lasted about a month. The propane for a similar period would have cost us about ½ that, but would have required we carry 9x30 lb tanks over the estuary sands to the tower each month. The one jug was much easier to carry.

The one problem with this system is the capital cost of about $12,000 – for a life guaranteed at 5000 running hours. Our use is right on the ragged edge of economic justification, but for sites that have to be serviced by the likes of helicopter, the price is easy to justify.

Bottom Line on Power at a Distance

Keep the total amount of power you use as low as possible. A camera and radio transmitter, coupled with a small utility board that turns things off when the light fails, can make even a battery-driven system last quite a time. In the end, the power generation can cost you more than the camera (and IP transmission system) and cause more headaches than any other aspect of the operation.

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