Sustainable energy and environment

A part of Port Augusta Renewable Energy Park (PAREP) Photo taken using my Mavik Mini drone 2021/12/19. (Sundrop Farm can be seen on the far right. Click on the image to see in high resolution.)

A wind farm   Just some of the turbines of hornsdale Wind Farm Photo taken using my Mavik Mini drone 2021/09/23 The photos above and on the right show fairly typical examples of a South Australian solar farm and wind farm. The striking difference between the two installations is the way the solar panels almost entirely cover the ground while the wind turbines take up very little land and farming goes on around them. I have summarised the problems associated with wind farms and I've written about the integration of solar with other uses elsewhere on these pages. On this page I hope to provide some comparison between the advantages and disadvantages of both forms of renewable energy from an environmental point of view. At the time of writing there can be no doubt that the world needs both wind and solar power if we are to displace fossil fuels, and there can be no doubt about the urgency of that. Home Top Index Wind and solar are a good combination   One day's generation in South Australia, 24hrs to 9:30am 2022/10/27 Graphic credit OpenNEM Wind energy can be available at any time of the night or day, solar power is obviously only available during the day, and is most plentiful in long sunny summer days and least plentiful on short cloudy winter days. If there is no wind there is no wind energy. The graph on the right is a good example of how wind and solar can combine very well. In the particular 24-hour period during the southern Spring there was apparently not a lot of wind during the day, but abundant solar power (yellow on the graphic), then there was plentiful wind power (green) over most of the following night. Home Top Index Life time, environment, economics and discount rate Both wind turbines and solar panels could probably be made to last 100 years rather than just 25 years at little more expense. This would obviously greatly decrease the resources and emissions needed for their construction in the long term. A large part of the reason that they are not made to last so long is the way economics works. In the minds of economists the discount rate makes the life of an asset after about 25 years near worthless. I am no economist, but I believe it works something like this: Due to the cost of finance and interest rates on borrowings, the future value of an asset is annually discounted. If the discount rate is 5% then a million dollar investment will be worth $950,000 after one year, $902,500 after two years, $598,736 after five years, and $277,000 after 25 years (even though it could still have 75 years more life). With a discount rate of 7% the calculated future value at 25 years would be $163,000. So, in the minds of an economist, spending perhaps an extra 30% to make an asset that will last 100 years rather than 25 years is just not justifiable. But if our children and grandchildren are to inherit a world that is not greatly damaged we must start giving environment a higher priority than economics. (For more on discount rate see Wikipedia; The weight given to future consequences relative to present consequences, measured by time preference.) Another reason is that both wind turbines and solar panels are still being developed and improved; a 25-year-old wind turbine in 2022 is superseded technology. Home Top Index A comparison of the environmental standing of wind and solar power Both wind turbines and solar PV panels have expected lives of around 25 years. A wind turbine is expected to 'pay back' the energy used in its construction in about six months; a solar panel will take something like two years. Power transmission lines kill birds - the birds that are killed typically don't see the wires and collide with them. Most wind and solar farms in Australia have been built near existing power transmission lines, so as of the time of writing great lengths of transmission lines have not been needed to connect farms with existing lines. This may change in future as new transmission lines are built to dedicated renewable energy zones with the existing high capacity grid. Land use in wind and solar farms As can be seen in the photo of Hornsdale Wind Farm above, little of the land within a wind farm need be taken away from farming (or other previous use including stands of native vegetation). Access roads need to be built and each turbine has a 'hard stand' around it, but the great majority of the land is untouched. Also as can be seen above, this time in the photo of the Port Augusta Renewable Energy Park solar farm, the land beneath the solar panels is usually completely cleared. As of the time of writing little thought or planning seems to go into the long term care of the land beneath Australian solar farms. Solar power can be combined with agriculture in agrivoltaics and to provide valuable shade in car parks and other places. Recycling and reuse of materials Both solar panels and utility-scale wind turbines are so new that no great numbers of either have needed to be scrapped, recycled or reused. I know very little about the recycling of solar panels. Wind turbine towers are often made of steel, which is readily recycled. The electrical parts would be recycled for their copper and other valuable metals. The gear-boxes are mainly steel - again readily recycled. The concrete bases of wind turbines will, in most cases, be left in place - they are environmentally inert so I can't see them being a problem. Wind turbine blades are made of plastic composites and are more challenging to recycle, but several wind turbine manufactures (at least Siemens Gamesa and a French consortium) were developing blades that were fully recyclable at the time of writing (January 2022). Of course the need for recycling would be greatly reduced if the blades were made with a 100 year life span, rather than a 25 year life span. Aesthetics Wind turbines are conspicuous from a great distance; not only are they tall but they are often built on the tops of ridges. Solar farms cover large areas with flat panels. Aesthetics, like beauty, is 'in the eye of the beholder', but I can't see any beauty in a solar farm while I see wind turbines as graceful and elegant. Of course this is entirely a personal opinion.

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