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Alternative power components

On this page I thought we could have a look at the main components a system is comprised of and some of the basics about driving a system.

The information here is very generalised and intended to be a start should you wish to research further.

A basic system will entail:

 
     
     
 

Deep Cycle Batteries

Batteries come in many shapes sizes and types generally a house system will use flooded cell deep cycle batteries of 375Ahr capacity or greater.

Sealed batteries are sometimes used but cost usually tends to steer people toward flooded cells.

Sealed batteries have the advantage of being maintenance free and do not usually require equalising charges, which is basically a controlled over charge usually performed monthly to stir up the flooded batteries acid as it tends to settle out or stratify. The charging system is usually configured to perform this task automatically.

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Charging System

Solar panels (Photo voltaic), wind turbines, hydro power, steam, gas turbine, DIY or comercially built, steam engine, stirling engine (see whispertech, regulation built in) petrol, diesel, or alternative fuel generator. Could possibly be your top secret magnetic perpetual motion motor utilising nano trilithium probe technology © (thanks Graeme) with bipolar quasi phase laterally split diode rectification harnessing the earths magnetic fluxes.

Whatever your energy source is (hopefully not Nuclear as it SUX big time - sorry, had to get that in somewhere) it is fed via a regulator to charge your batteries. See system types for the more terrestrial types of energy sources and please email me if you have discovered something else!

So far I'm still managing to keep an open mind.

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Regulators

The main purpose of the regulator is to stop the batteries from overcharging and boiling off all their electrolyte (Acid). The more sophisticated types perform monthly or sometimes more frequent equalisation charges for the flooded cells. A good regulator will charge the batteries in 3 or more step process, ramping the battery voltage up high for a predetermined time then backing the voltage off to a float level.

DO NOT EQUALISE SEALED CELLS unless the manufacturer recommends it. They don't usually need it or like it.

The regulator on a PV system will limit the power the batteries receive from the panels when they are charged. The old fashioned types simply cut the power all together. The modern ones do the same but many times a second (pulse width modulation or PWM) and will hold the battery voltage at different levels depending on the batteries state of charge.

A regulator for a Hydro or WInd turbine will dump excess power into a dump resistor. Turbines need to have some load on them to stop them over - revving.

In recent years Maximum Power Point Tracking (MPPT) regulators have become available. I have recently installed one (Outback MX60) on the Wattshop system and will be posting results on these pages when we have accumulated some data.

Their principles of operation are a little too tech for discussion here, and the manufacturers data sheets will probably explain it better than I. Suffice to say that they will give a gain in a PV system depending on conditions by better matching the electrical characteristics of the PV solar panels and the batteries (impedance matching is how I think of it for those who have dabbled with electronics) An analogy would be the way a transmission in a vehicle matches the output power from an engine to the speed and torque the vehicle requires at the wheels.

 

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Inverters

The inverter converts the stored Direct Current (DC) energy in the battery to 230 volt 50 Hz Alternating Current (AC) in my part of the world. This is the same as you would get off the grid, only better. Voltage and frequency will be different if you live in the United States for example.

There are two main types, Inverter only and Inverter Charger. Other versions on these two themes usually have to do with the output electrical wave forms. There are two types, SINEWAVE and all the others.

A good quality sinewave inverter will give you a better quality of power than you can expect off the grid (I didn't say quantity!) If you want to subject your equipment to anything other than a sinewave you'll have to buy it somewhere else - I don't need the grief. Many people have got away with lesser inverters for years but as the stuff people are plugging in and has got more sophisticated, read expensive, I don't go there.

What to look out for in an inverter

  • SINEWAVE OUTPUT!
  • Reasonable surge capacity
  • Charging function?
  • Standby or sleep function - this will save a lot of energy from your batteries if the inverter goes to sleep when it is not required. The inverter will automatically start itself when it detects that power is needed.

Don't think that you need a huge inverter because you want to run power tools or other high drain devices. A good quality inverter will be able to supply as much 3 times its continuous rated current for a few cycles to provide enough current to start motors etc and can be run "overloaded" for short times.

Most people will find a 2000watt (2kW) inverter more than adequate. I have been running our house on a 1.5kW machine for the last 5 years without tripping it out on overload.

2009 update; now in our 8th year on alternative power we have found the limit of this machines capabilities, the vacuum cleaner, espresso machine, and toaster all on at once will trip it out! Not surprising really and easily avoided :-)

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Inverter Chargers

The inverter charger is a handy beast in that you can feed it electricity from a generator to charge the batteries when the sun, wind or whatever is not being co-operative. Some of the ones we sell have a function where they can start the generator automatically when the batteries require charging assuming the generator has auto start capability.

These, IMHO, are probably the best way to obtain a battery charger for your system. My reason for saying this is you can be sure the battery charger is designed for charging deep cycle batteries and not automotive, forklift or some other type of battery which could have completely different requirements. Unfortunately I am speaking from personal experience.

The other advantage: with a decent generator and inverter/charger the batteries can be bought back up to full charge relatively quickly. This can save a battery bank from being damaged and reduce the overall size of the battery bank required.

While the generator is feeding the inverter/chargers we sell, the charging system takes what it needs from the generator and makes the rest of the generators capacity available to the house. This is a good time to do the ironing, vacuuming, or operate high drain equipment that would otherwise hammer your batteries.

If the charger detects that the generator is struggling, it will back off until the generator is coping with whatever demands are being placed on it. If someone wants to buy my old but perfectly good inverter off me, I will be replacing it with an Outback inverter / charger.

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Monitoring / Metering Equipment

The most basic being a volt meter indicating the battery voltage. While better than nothing, it will not tell you a whole lot. Some of the more expensive regulators will store information about battery condition and how much power has passed through them into the batteries. My new Outback MX60 stores the last 60 odd days power production from the PV's in its memory. NICE.

The best device, I think, is the EMETER in one of its various guises. This expensive but cunning little device can tell you:

  • Battery voltage
  • Amps flowing into or out of the battery
  • Amp hours remaining in the battery

...and can be configured to read like a fuel gauge giving a percentage reading, or calculate how much longer the battery will last at the rate you are consuming power. I prefer the fuel gauge type configuration.

But that's not all:

  By the use of a clever algorithm, the Emeter will take into account the battery capacity, depending on the rate of discharge. A battery supplying a large amount of current will not have the same capacity as the same battery supplying a smaller current. It's a case of the more you take the less you will get. This and the fact the Emeter will take into account the batteries inefficiencies is where the Emeter leaves other amp hour accumulated meters in the dust with flat batteries. Wish I had got mine right at the start!

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Outback Products


No Im not been paid to plug Outback equipment (though I'd be happy if that changed!!)

Yes I do reccommend, sell and install their products.

Why do I reccommend them?

  • I believe them to be robustly constructed
  • Only inverter charger I have available that is bug, dust and almost water proof
  • Cheapest inverter charger I have available - the nearest comparable product costs considerably more
  • They have a great design philosophy, the inverters are field servicable
  • Most importantly to you the customer, they are value for money

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AC or DC House Wiring?

For a house I would suggest it is far more practical to go to an AC system as I believe it to be safer and cheaper in the long run. I will concede that it is not quite as theoretically efficient but I think the losses are not great enough to go to the hassle of pure DC. Most DC systems I have seen probably had the equivalent losses due to undersized cabling.

It is my opinion, DC systems belong in boats and camper vans where cable runs are short. In a house situation where cable runs are much longer, an AC system is easier and cheaper to size cables appropriately and provide electrical protection for. Reason being, the high current low voltage power needs much larger cables to get it from A to B without losing all its oomph down the length of a cable.

The dynamics of electricity can be readily compared to that of water down a pipe. I.e. low pressure (volts) high flow water (current) needs a big pipe.

The other main advantage of AC is most of the worlds electrical products have been designed for 120 or 230 volt AC systems and sourcing appliances, light bulbs, & protection devices for other voltages and current types is usually expensive and sometimes difficult.

If you're a purist and insist on going the DC route, I wish you luck and ask that you are very careful in sizing your cables and obtain appropriate electrical protection devices rated for DC working. Most AC breakers are not up to the job. While the risk of electrocution is probably almost nonexistent with a DC system under 30 volts, the risk of fire, I think, is probably 10 to 20 times greater as the electrical currents to do the equivalent amount of work are this much higher than in the higher voltage AC system. It is the magnitude of these high currents that creates the undesirable heating effects in connections, undersized cables and fittings designed for AC.

The protection devices have to have much larger ratings for the larger currents that will be flowing so they are not as sensitive to fault conditions. The same applies when selecting inverter voltages and I always opt for 24volt systems or higher. DC currents are inherently harder to stop than AC and switches designed for DC are usually a lot beefier than their AC counterparts.

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The Watt Shop - Alternative Power  |   PO Box 342, Kaeo, Northland, New Zealand  |   Phone 021 784 678

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