Thursday, 16 April 2015

The difference between Power and Energy

Image result for man on treadmill cartoon

Power and energy are two words that are thrown around a lot in the debate on energy. Val Martin of EPAW helps explain the difference between the two :

There is a huge difference between energy and power as Robert Bryce pointed out in his book on the subject, “Power Hungry”.    There are three sources of energy on Earth, Solar from the sun to grow plants stored over millions of years as fossil fuel, tidal from the gravitational influences of the moon on sea water and nuclear from the fact that E = mc2. There are non quantifiable sources of energy, falling leaves, horses, people, rain water, wind, explosives and lightening to name a few. There is a misconception that energy is power. While the sun and nitrate in fertiliser is required to provide the energy to grow plants, the feebleness of sunlight and the intensity of Nitrate explosives make it difficult to use it to provide power homes, transport or electricity. The electricity grid needs a constant reliable source to provide the power to drive cookers, electric power tools, welders etc. Likewise a loaded lorry going up a hill needs a very intense source of energy carried with it. Lightening is very intensive, but incapable of conversion.

Let's say a retired couple have a family saloon petrol car. Government introduces a law that the engines must be removed and replaced by a horse connected to it and controlled by reins through holes in the wind screen. Say the horse = 1 horse power (hp) and the car = 12 HP and the car is required for 2 hours a day, then theoretically the daily energy potential of the horse is 24hp (24 x 1) which is enough to power the car. The problem is that the horse is restricted to an average speed of 7 mph, he will only move 24hrs x 7mph = 168 miles in one day. The car can move 24hrs x 50mph = 1,200 miles. On a steep hill the horse may fail. Moreover the travel times for the couple will greatly increase and there may be no heating or lighting system, not to count rest times for the horse. The misconception with wind energy is to count the total potential output over one year as the actual useful output. 

A test of any energy source is if it can work on its own, independent of other sources. If it cannot, the likelihood is that it is a passenger on the system. There is no agreed scientific way to measure the contribution of wind energy on the grid.  

1 comment:

  1. The UK energy market uses electricity for industry and lighting and gas for home heating and cooking. In 2008, they committed to the EU 20% renewable target which translated to 15% there. Whereas France and Nordic countries use electricity for most energy needs, Britain differs with its use of gas too. In fact the term “energy” in the UK is taken to mean electricity + gas and many utilities have common offices. Because there is no such thing as renewable gas, the entire renewable targets fell to electricity. Renewable supports were calculated at 89 billion pounds from 2013 to 2020. It is £68 now per year per household rising to £225 according to official figures for the levies alone. The wholesale strike price for electricity is £45 - £48 for conventional electricity, its £90 to £95 for on-shore wind and £150 for off-shore wind. Bio Mass is 105 and nuclear is £96. The shale gas revolution in America has given a glut of coal in Europe and despite the high Russian tension, the price of gas has been falling in 2014/15. For the domestic consumer, the hikes in electricity have been balanced by a reduction in gas and of course there is a £400 winter fuel allowance payable to everyone of pension age irrespective of income.

    The problem is that there is no balance for industry. They use nearly all electricity and electricity is bearing the brunt of the cost of renewable energy. , Industry must compete internationally. If this cost burden leads to industry moving abroad, the co2 emissions of the UK will drop, giving cause to celebrate, but the country will be poorer with less employment and poor balance of trade. It was very unfortunate to apply the term "energy" to renewable targets, without defining what energy actually is. As posted in the main article above quoting me and Robert Bryce the wikipedia definition is ------- "a property of objects which can be transferred to other objects or converted into different forms, but cannot created or destroyed." ------- Wind energy cannot be created or destroyed, the question is can it be converted? I claim it can be converted into electricity, but not into mains electricity. This is key to understanding how such a monumental mistake was ever made. As Robert Bryce pointed out in his book, ----------renewable energy is "energy" but we have no need for energy, we need power and wind energy is not power.--- So British industry must pay levies to have renewable energy in its electricity mix, but that energy is useless, only the power component is of use, the energy component is a passenger.