[alancalverd (OP)]

Wind turbines convert at best about 70% of incident wind power to mechanical power, though this is only over a narrow range of wind speeds. 50% over all conditoins is a sensible figure. About 90%  of this is converted to electrical energy, with 5 - 10% further losses in distribution transmission and maintenance ( not just ohmic and transformer losses, but including routine helicopter inspection of power lines and the replacement of pylons, switchgear etc.) to the consumer. 0.5 x 0.9 x 0.95 =  42.75% overall efficiency. Where does the rest go? As heat.

Solar panels probably convert 20% of incident radiation to electricity. In doing so they occupy land that would otherwise be used for crops (which absorb carbon dioxide) and distort drainage by forming an impermeable sheet over the soil. About half of the remaining 80% is reflected as longwave infrared, contrtibuting to atmospheric warming by radiation, and the remainder is removed by convection, heating the lower atmosphere (I regularly fly over a solar farm on the approach to my local airfield - what a ride!). Allowing 5% transmission losses once again, we have a system that generates four times as much heat as electricity!

Now put that electricity into an electric car. You can recover about 90% of the input energy from a new battery,  and maybe transfer 90% of that to the wheels, but by the time the battery needs replacement (and never mind the energy cost of making a new battery) it is down to 50% recoverable capacity. Say over the life of the car, a total of 60% of input energy is useful, 40% wasted as....heat!

Whatever the merits of renewable energy, it adds a heck of a lot to global warming!

[pensador]

Most Humans would agree energy from the sun causes warmth on the planet, by using the suns heat we do not increase the amount of heat on the planet or contribute to global warming in any way. Global warming is being caused by most humans who burn fossil fuels releasing carbon dioxide.

Wind is driven mostly by the suns heat causing convection currents and the coriolis effect, we can convert this wind power using various designs of wind turbine, which have different efficiencies. The efficiency of a wind turbine, is dependent on the wind speed it is designed to operate at. At less than about 10 knots of wind they are pretty useless. A link covering some aspects of wind turbines https://greenliving.lovetoknow.com/Efficiency_of_Wind_Energy
The payback time on wind turbines can result in many wind farm companies going bankrupt

Solar panels are becoming increasingly more efficient the word record was 46% efficient, and your figure of 20% is for old technology https://en.wikipedia.org/wiki/Solar_cell_efficiency

If the deserts were to be covered with solar panels, land that produces nothing could be transformed into a useful resource for countries with no oil, or other means of generating income. If power cables were placed under ground, they would receive less damage from storms and trees etc falling on them.

Solar panels require little maintenance compared to wind turbines, but they are not the only renewables contributing to the worlds power supplies.

One side effect of global warming that may affect your flying is that as the oceans get hotter the winds get stronger. Category 5 hurricanes become more common, and you aint going to be flying in one of them, and if your plane isnt tied down or flown out of harms way, like what they do in the carribean, your aeroplane is going to get blown away, end of hobby!

[alancalverd (OP)]

Category 5 hurricanes become more common

Their frequency has actually decreased over the last 100 years, although the damage done by each has increased due to more people investing  in more structures in the hurricane landfall regions.

[Janus]

Whatever the merits of renewable energy, it adds a heck of a lot to global warming!

As does any method of "producing energy".  There will always be inefficiencies that create waste heat whether is by solar or digging up and burning coal.   But burning fossil fuels also adds to the problem by taking carbon that has been sequestered and putting in the atmosphere as CO2.   There is no "perfect solution" to global heating due to energy production, ( other than reducing the energy production itself),  but the lack of a perfect solution doesn't mean that some methods are less problematic than others.

[Bored chemist]

Whatever the merits of renewable energy, it adds a heck of a lot to global warming!

No, it doesn't.
"helping to stem the tide of ignorance"
Cough!...

The energy from the Sun is converted to heat.
It doesn't change the amount of heat if you get it to do something useful - like run your computer- on the way.

It's important to distinguish between the heat released by burning fossil fuel from the effects of carbon dioxide which trap vastly more heat from the Sun..

[evan_au]

I vaguely recall seeing figures something like:
- In the early days of petroleum production, it took the energy of 1 barrel of oil to produce 100 barrels of oil
- We have used up most of the deposits that pump themselves out of the ground (and Saddam Hussein set some of the others on fire).
- So we have to go after deeper deposits, smaller reservoirs, further underground, or further out to sea
- New wells are costing something like 10-20 barrels of oil to produce 100 barrels of oil
- If you add in carbon capture and sequestration, this involves pumping carbon dioxide under high pressure into deep rock strata, at an estimated cost of 30-40 barrels of oil per 100 barrels of oil.
- This is a trumped-up excuse for throwing more good money after bad!
- The environmental costs for defrosting and mining Canadian oil shale deposits were horrendous!
- I can't guarantee the numbers, but the trend is clear!

So we have the problem of declining efficiency and increasing costs of the petroleum industry

And we are comparing it to the increasing efficiency of renewables
- Hydro power already has amazing efficiency, so it's not improving much today (but it is becoming more available in small units)
- Wind turbines are improving efficiency with larger units
- Solar cells are improving efficiency with improvements in production techniques, and potential introduction of tandem cells that absorb a broader part of the Sun's spectrum (tandem cells are currently more expensive, so only used for high-value applications)

So our goal for the environment should be to invest more in the improving technologies, and conserve the fossil fuels for things that don't currently have an alternative
- Aviation and trucking are such applications (but I see that a demonstrator electric light aircraft was flown at a recent aviation show)
- That means investing in wide-area transmission grids to share the generating capacity
- And ideally, electricity storage (preferably hydro or similar efficiency)

[jeffreyH]

Renewables may generate heat but don't trap it in the atmosphere. That is the most important part. Letting the excess heat get out. The current heatwave that has just occured across Europe should scare the living daylights out of everyone.

[alancalverd (OP)]

Indeed it does, but nobody has any intention of doing anything useful about it.

[evan_au]

One of the first applications of steam engines was to pump water out of coal mines.
- After using up the "easy" coal deposits, they needed to mine less-accessible deposits
- And mines were always filling with water
- So the industrial revolution started with coal-powered steam engines making it easier to mine more coal
- And another early application was coal-powered steam engines that made it easier to move coal (and people, and other goods)
- A positive feedback loop that resulted in thick smog in many cities
- Whole communities being built around dangerous underground work, with risks from silicosis, tunnel collapses and explosions
- And environmental damage from mine tailings, and the occasional out-of-control fire that sets the coal seam on fire

A similar effect occurred with petroleum/gasoline
- With liquid fuels being used to power mining equipment, power refineries, and transport liquid fuels.
- At least liquid fuels produce less CO₂ than the same amount of energy from coal
- While explosions are still a risk, there is much less underground work, so less production harm to humans
- Risks to the public reduced when lead compounds were banned from petrol
- But there is still a lot of soot from diesel engines

Natural gas (methane) is less carbon-intensive than liquid fuels
- Many of the "easy" deposits have been used up
- Now more energy-intensive "fracking" must be conducted to reach the remaining gas

It would be interesting to see figures on just how energy-consuming these energy-producing industries have become (including the renewable ones)...

[jeffreyH]

Indeed it does, but nobody has any intention of doing anything useful about it.

Well with big Orange Orangutan man stomping around the US and declaring coal a fuel of the future it is hardly surprising. No one is doing anything about him either.

Do we deserve a future?

[syhprum]

Hydro power plants are a great source of danger from wasting agricultural land to making breeding areas for mosquitos and killing large numbers of people when dams burst.
They kill vastly more people than nuclear but are beloved by the green mafia.

[Bored chemist]

They kill vastly more people than nuclear

They have both killed of the order of 10,000 to 100,000
https://en.wikipedia.org/wiki/List_of_hydroelectric_power_station_failures

https://www.newscientist.com/article/dn20403-how-many-died-because-of-the-chernobyl-disaster-we-dont-really-know/

There are about 450 Nuclear plants in the world generating about 10% of the world's electricity and over 8000 Hydro power ones (over 1MW) generating about 17% of the world's electricity.
On a MW by MW basis the death rates are fairly similar.
It's hard to do a like for like comparison based on numbers- there are lots of small hydro power projects but few small nuclear stations.

[evan_au]

there are lots of small hydro power projects

In the days before steam engines, almost every  town had a small hydropower project, using a local stream and a water-wheel to mill grain. In some places the blacksmith also used hydropower to operate his machinery.

[alancalverd (OP)]

Not a good idea to compare an accurate figure of directly attributable deaths with "we don't really know" in a science forum!

Hydropower only impoverishes the poor, so it's OK. They can leave their farms and live on the streets. And it makes work for archaeologists, surveying and preserving old stuff that nobody wants, before it is flooded.

I've often wondered about the coal economy. Considering the vast number of trees cut down, turned, sawn and transported to make pit props, then the huge quantity of steel manufactured and bashed into shape to line tunnels and make railways for transporting coal, plus the amount of human and animal sweat required to dig the stuff out and move it to the surface, does it actually produce more energy than it consumes, or is it just in a more convenient form?   

Anyway, to turn to directly attributable deaths, more people were killed by a single coal tip landslide at Aberfan than Chernobyl. Coal mining directly causes about 1 occupational death in 7,000 man-years, compared with the most pessimistic estimate* of 1 in 20,000 in the nuclear industry.


*problem is that radiogenic cancer is indistinguishable from any other cause, and takes about 10 - 15 years to manifest. With a natural incidence of fatal cancer around 1 in 3, and the annoying statistic that nuclear industry workers actually live longer than average, it's rather difficult  to unravel this one.     

[pensador]

Category 5 hurricanes become more common

Their frequency has actually decreased over the last 100 years, although the damage done by each has increased due to more people investing  in more structures in the hurricane landfall regions.

No it hasnt, You are just being argumentative.
https://en.wikipedia.org/wiki/List_of_Category_5_Atlantic_hurricanes. The jet stream also affects the formation of hurricanes via knocking the tops out of them before they form. This also skews the figures, the oceans are getting hotter, the likelihood of stronger storms is increasing.
renewable energy does not increase the amount of green house gas in the environment, that prevents heat escaping from the planet. https://www.bgs.ac.uk/discoveringGeology/climateChange/CCS/man-madeEffect.html