Monday, March 14, 2011

Carbon Emissions and Hydo-Electric Dams

 It seems that every time electricity consumption is mentioned, the writer links electricity use to carbon emissions. So what do they base this on? 
Evidently they have not heard about hydro-electric power generation, or else they are ignoring it. 

These writers take a swipe at power dams in passing by mentioning fish migration blockage. Clearly they have no real understanding of how many power dams are designed.
Fish ladders have been used for over half a century that I know of. Possibly longer, if you really delve into it.
A fish ladder is a series of shallow pools that flow slow enough and are not so high that migrating fish cannot jump them.  Anyone who has seen bears fishing in a west coast river will realize migrating fish can and do jump a barrier several feet in height. The bears are smart enough to realize if they stand in the rapids they can catch jumping fish without the use of nets. 
Many dams do in fact incorporate fish ladders in their overall construction.

I read somewhere of plans to demolish an existing power dam on the Snake River in Washington on the border to Oregon state. This is a branch to the Columbia River. Detractors have for years been complaining that the dam is preventing fish migration. Yet a Google search revealed that these dams do in fact already have fish ladders.  Construction dates back to 1933

The dam already exists and is not producing any carbon emissions. Furthermore the dam has now been in existence so long that removal of the dam will have major effects on upstream farm irrigation.

Given that a lot of diesel powered machinery will be used to cart away the debris from the demolished dam this really does not make a lot of sense.

If these greenie fanatics really care about carbon emissions there are other options available.
  
The argument that the old dam turbines are inefficient may be valid but turbines can be replaced and upgraded.  .

The past century was marked by mega projects where everything had to be bigger and better .Then came along an idea that said ‘small is beautiful’
Gradually power engineers are realizing that a super grid spanning the continent may be too expensive and have too many inherent problems.
The new thinking being many small power generators that are dispersed can be just as effective as one big power generator feeding power to locations thousands of miles away.
New designs can mean hydro-electric generation cans co–exist with fish migration. And it may even mean power generation is now possible from streams that were previously considered unfeasible.
Valid concerns about old aging dams not being seismically sound are another valid concern. Smaller dams or better yet dam less construction definitely deserves more study and development.

Hydro-electric is in effect using solar power but indirectly. Sun energy is what produces evaporation which in turn leads to rainfall that results in streams running down to the sea.  If you look at how  the production of the solar cells and the necessary electronic controls plus the manufacture of toxic lead acid batteries  it becomes obvious that  a hydraulic power dam is less polluting to the environment.

Recent developments in water power means we can now generate power from flowing water without damming the creek or stream or impeding fish migration.  Much research has been made in tidal water power generation which involves horizontal water flow with only a modest rise and fall in elevation. Some of these tidal generators do not rely on elevation at all.  These designs could extract power from flowing rivers and streams where there is no possibility of a vertical dam drop nor would they impeded fish migration.

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Why not use 12v DC for Off-Grid


Many people when  first contemplating  going off grid  expect to use  12V DC  power because they  see 12V batteries  and 12V lights used in RV; so they think this is  how  power is used in  off-grid applications.  It’s is a reasonable assumption but fraught with technical problems. Except for lights, few 12V appliances are durable like their 120V AC household equivalents.  Take a 12V coffee maker as a common example. You can buy such devices in RV shops and truck stops. In order to heat up enough water for two cups or one big mug full takes a certain amount of power.  300 watts is about the minimum   that will heat up water in anything resembling a reasonable length of time. 
At 120V the 300 watt coffee maker will draw 2.5 amps. At 12V DC the coffee maker needs to draw 25 amps to heat up the same quantity of water in the same length of time.
2.5 amps only require a thin wire.  The #16 gauge wires often used in automobiles is rated to carry 10Amps so it is perfectly safe and remains cool in use.  However, in order to carry  25 amps requires at least #12 gauge wires  provided  you use high temperature  insulation or better yet  #10 Ga wire which is rated for 30amps.
The 12V appliance will not last as long because the construction does not stand up to prolonged use and typically fails in a few months instead of lasting a few years as is common with normal household appliances.  The same can be said for all 12V appliances.

A quick review of products reveal   the cheapest 12V coffee maker is around $35 whereas the cheapest 120V AC model is $12.95 not to mention which the range of choices for 12V models is limited while the number of AC products in almost limitless by comparison. There is also a wider range of styles available.  A similar situation can be seen for just about any product you care to mention. 12V appliances are often only found in specialty stores.

Another aspect has to do with wire losses using the same example of a 300 watt coffee maker and let’s say there is 25 feet from the power source to where the coffee pot is plugged in.  You need to use #10 Ga wire and this results in a 10.79% loss in the wiring.  This will mean it takes that much longer for the water gets hot and you are wasting 10.79% of your solar power.
Let’s look at the losses for the 120V coffee maker. Voltage drop at 120V is only 0.69% and you can get away with using #18 Ga wire. The electrical code does not permit using any smaller and in any case such small wires are too fragile for general wiring work.
So it should be obvious that not only can you use smaller wires which cost less to buy but the losses in the wire are less than if you used 12V DC.
Conventional 120C AC wiring is very common and the fittings are readily available in just about any hardware and home repair supply stores. This makes it attractive due to low price and being readily available. If you are not sure how to wire it there are any number of self help guide books including guides as to what the code calls for.
If you choose to wire with 12V you will need specialized hardware, fuses and or breaker or breakers. In many cases special  (read expensive) terminals bus bars and definitely larger and thus more expensive copper wires. The cheap stuff is simply an invitation for a fire down the road.
Inverters in varying sizes are available at reasonable cost. It is possible to get inverters able to power entire house holds.
There are still cheap junk products in the market but there are also plenty of quality brands with a long history of excellent performance.  One hint never load the inverter to 100% of the rating. If you need 1000 watts select a 1500 watt inverter because the inverter will run cooler and last longer.

Some of my designs are even intended to power air conditioners, assuming you have a large enough battery bank and recharging capacity.
An added benefit to wiring for 120V comes from the fact you can start up a regular genset and feed this power right into the off-grid home wiring circuits. Even the best solar system will see cloudy days and the battery bank will get depleted eventually.
Having the ability to run a back-up power source in those conditions is a benefit.

Inverters will automatically shut down when the battery voltage goes low. This will protect your battery from excessive discharge and subsequent damage.
Having a DC load directly connected to a battery may result in permanent damage to the battery if the DC load continues to deplete the battery below safe levels.
 
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