CAN "SUSTAINABLE ENERGY SYSTEMS" RUN THE WORLD??

Other than nuclear. I don't think so. Let's see.

You can allow that on average a person in a modern industrial society consumes about 750 Watts per hour, continuous day and night.

TIDAL POWER Let's consider the realities, and an illustration.

We would require a bay going inland for a kilometer for storage to run the system. And the bay would need to be one metre wide for every kilowatt we generate. That's near a metre wide per person.

So to tidal power a city of 3,000,000 people we would use 3,000,000 metres of coastline with a bay running inland one kilometer. That's 3,000 kilometres, or around 1,800 miles of coastline.

This is the arithmetic.

One litre of water falling 100 metres every second generates one kilowatt of power . (It's a bit less than that due to inefficiencies in the generating plants. Efficiencies vary from about 70% to 90%. and for tidal 80% is considered good) ....or you need 100 litres per second falling one metre to generate one kilowatt.

A one metre average fall for the water is about what you get from a 3.3 metre total tide variation, or about 30% of the total tidal variation. We'll use this tidal variation of 3.3 metres or about 11 feet for the following exercise.

To store the tidal water moving from the usual maximum high tide to minimum low tide the wall has to be at least 3.3 metres high.

Let's consider generating one kilowatt.

Volume of water for one tidal cycle of 6 hours (it's actually 6.25 but we are keeping things simple)
becomes:

100 litres x 3600 (seconds in an hour) x 6 (tidal cycle) then divide by 1000 to give tonnes

We get a volume of 2,160 tonnes of total storage for the system or 2,160 cubic metres per kilowatt

Now the water is 3.3 metres deep and if, for the exercise, we consider a one metre wide strip of water backing up and going inland

Then we have: 2160 cubic metres divided by 3.3 = 654 metre long strip of water running inland for our storage.

At 80% efficiencies the strip needs to be increased to 817 metres long, or getting up near a kilometer.

With double the tidal variation and you would need 1500 kilometers. Same 3.3 metre tide but we have a bay that runs inland say five kilo metres then you need only 600 kilo metres of coastline to run our city.

Around the world there are government funded tidal energy R&D projects and various other government funded toys, but there is only one serious tidal operating system and it's in France. It's across the mouth of the La Rance River. Tidal variation is 8 metres and goes up to 13.5 metres for periods. That's 25 feet and to 44 feet, making it a rare and near perfect site.

The La Rance tidal power station was built in 1967. On today's figures it seems to have cost around $12,000 per kilowatt of generated power. It generates on average 70,000 kilowatts or enough for maybe 100,000 people. $12,000 per kilowatt is a about four times the price of a similar output nuclear power plant and about eight times the price of a coal plant.

Running on tidal energy your power bills would go up at least four fold.

WAVE ENERGY Let's consider the realities.

A long continuous wave power-generating machine producing say 2,000 watts per metre, on site (Which is actually pretty optimistic.)

Means Sydney Australia, with a population of 4,500,000 would require 2,250,000 metres of coast line, or 2,250 km. That's like Melbourne to Brisbane. It's like San Diego to Seattle, or Miami to New York.

Brisbane population 1,760,000 would require 500 km. That's from Brisbane to way past Rockhampton; or Seoul to Hiroshima.

Using all of both Eastern and Western US coastlines would not even power Los Angeles

There are no commercial units operating anywhere in the world. And again, just like tidal power, there are plenty of tax funded R&D projects and lots of toy units around.

There are plenty of well considered estimates of power output. In turns of coastline they range from 100 watts per metre of coastline to 3.6 kilowatts per metre. Theoretically these production figures could easily be doubled and then the length of coast line would be halved.

.

There is one small operating test unit in the world. The rest are all "being considered"

limited and rarely practical

DEEP HOT ROCK ENERGY EXTRACTION

No working installation anywhere (so is currently snake oil.) Much publicity but seems very impractical for many reasons. See Priority One for comments.

currently wishful thinking, most likely impossibly

SOLAR VOLTAICS .

Power prices have come down considerable but have now tended to level out. For commercial power generation, the power they produce is around ten times the cost of nuclear,coal or gas.

Now readily available. However for industrial power, costs will continue to be prohibitively expensive for at least many years.

viable only for small non-industrial applications

CONCENTRATED SOLAR VOLTAICS

Incredibly expensive and no energy storage system available.

Maybe close to commercial fossil fuel and nuclear generating costs is could happen in a few years. The system has extreme cooling problems. It is currently utterly impractical to store generated energy to cover unpredictable periods of cloud cover.

still hypothetical

CONCENTRATED SOLAR THERMAL

About a minimum of four times the cost of commercial fossil fuel and nuclear generation and no energy storage. Is currently utterly impractical to store generated energy to cover unpredictable periods of cloud cover, with not even hypothetical answers available. Power costs are falling but unlikely to be less than three to five times nuclear and coal power costs. Probably has a valuable application in remote areas away from any power grid system. They are cheaper than diesel electric power at current oil prices.

still somewhat hypothetical, other than limited application

WIND POWER

At close to commercial fossil fuel and nuclear generating costs is available now, but sites limited to "roaring forties" latitudes and a few rare wind encouraging land topographies. Power generated has risen rapidly to approximately 2% of World use. It's like a helicopter blade system turned on its side which results in enormous maintenance costs.

practical but limited

Solar, wind and "other renewables" to power the world?

I'm not hopeful. What do you recon?