Solar and wind are clearly viable, in the sense they work. Viable doesn't mean they make good solutions. Two scenarios are proposed for solar and wind are:
- "All of the above"
- WWS - "Wind, Wave, Solar". A 100%-RE future
Let's consider the 2nd first: WWS. The main weakness of wind and solar are that power sources are:
- very dilute. Wind averages about 2 watts per square metre. Solar peaks at about 200 watts per square metre (w/m) and averages 100 w/m. Read the sections on Wind and Solar in Renewable Energy Without the Hot Air.
- The sources are variable (or intermittent). There's no sun at night, less sun on cloudy days, and about 5 times more sun in summer than winter (in Britain). The ratio of winter to summer sun depends on one's latitude :- how far away one is from the equator. The further away, the less sun there is in winter. In Britain, solar' weakness is more a case that our maximum electricity demand peaks in mid-winter in early evening (5pm to 7pm) at about 54 Gigawatts. Our maximum demand is at a time when the sun has set, and annual solar output is at its lowest. In contrast, minimum demand is about half that (about 28 GWe): on a summer Sunday. If we make enough solar to wholly power us on that summer Sunday, it will still only make enough electricity to supply a tenth of our winter needs. So are we supposed to over-build 10 times as much solar as we need?
Even windy countries like Britain experience windless (or low wind) periods. For example 20 days at the start of September 2014 when wind was down to about a third its average. Because the sources are intermittent we'd need a lot of energy when there's no sun or wind. Wind-powered Britain would need 2 weeks backup. How much is that? Our average power use is about 40 GWe. Multiply that by 20 days, 24 hours a day, we have 40 × 24 × 20 × ⅔ = 12,800 Gigawatt hours (GWh). A truly astounding reserve supply of energy. We won't be making batteries to store it, don't have enough water to provide for pumped storage. Neither wind nor solar would work for Britain. Nor would any combination. We don't really have lot's of spare land, nor are we willing to damn our rivers. Hydro resources are almost maxed out. That leaves us wave and tidal power. This will be even more expensive than solar and wind but has different intermittency issues.
Renewable energy will not stop us using fossil fuels
The only sensible thing would be to switch on fossil fuel (gas, coal or oil) power stations to solve RE's intermittency issue. So renewable energy will not stop us using fossil fuels. In fact, Germany has seen no emission reductions for 7 straight years : 2009 to 2015 inclusive. Naturally green campaigners now want to stop us using any new fossil fuel resources, such as fracked natural gas. The natural gas we'd (actually) need to power their (imaginary) 100%-RE future is to be banned!
What's the point?
What's the point of RE if it does not really lead to the zero-carbon energy future RE advocates say they want? Is it really just a Trojan horse to con us into de-energizing with more expensive, unreliable energy (followed by consequent deindustrilization). Yes, that's what I believe the RE-agenda to be. People who know what they're doing want to deindustrialize. People who don't know what they're doing are just their useful idiots.
Renewable energy problems are glossed over
All these problems of renewables are glossed over by the promoters. They have basic spreadsheet and computer models which don't address real world concerns. Models which only exist to provide a thin gloss to befuddle critics and con more RE supporters. RE supporters are not serious enough to provide us with models that acknowledge the weaknesses of renewable energy. It is, in fact, a climate change denying crime to say there are weaknesses. Renewable intermittency is said to be a myth in hard-core RE circles. They deny the real world. No wonder they can't be bothered to model their supposed 100%-RE future!
RE is decentralized and trans-national, at the same time!
One set of RE-supporters say that a big reason for supporting RE is that control of energy will, in future, become decentralized. Each community will be able to power themselves and have control over their energy needs. A different set of RE-supporters say that intermittency is a myth at grid scale. That's because when there's no power in Britain, there will be an oversupply somewhere else, from which Britain can draw on, for example, from the Balklands. Nations will no longer be in control - there will be an international grid. How is it possible for one band of RE supporters to believe one narrative and for the professionals to believe an opposite? The answer's simple: RE is whatever you want it to be. It's more an aspiration for an alternative than an actual alternative. People project their dreams onto it. Their RE-future becomes what they want it to be.
So 100% renewable energy is unrealistic and undesirable.
What about all of the above?
Yet what's wrong with "all of the above" : nuclear, wind, and solar? The answer is: the more wind and solar built, the more fossil plant is needed to provide for sunless and windless periods, the less viable that makes nuclear power. Nuclear power plants provide power all the time at a pretty constant rate. The main problem they have is making too much electricity in early morning hours, too little during peak periods. Nuclear plants can be designed to load follow but that's not ideal - it makes nuclear power less efficient. Because nuclear provides constant power, there's no real point in harvesting wind and sun, as we just oversupply. At the moment, oversupplied RE is paid for. RE has priority grid access, meaning the grid must take it (and pay for it) whether or not it's needed. In times when RE is supplying, nuclear power would not be paid for. With RE on the grid, nuclear power would only get a fraction of the revenues it could otherwise get. More RE makes nuclear power less economically viable. In contrast, non-RE baseload power is essential to make RE work. RE needs nuclear power but nuclear power doesn't need RE. The argument against all of the above is presented by Peter Lang, copied to here: Every new investment in renewable capacity is delaying GHG emissions reductions.
The best, most efficient, non-carbon, electricity grid, is to aim for 100% nuclear powered grid like France with plentiful pumped storage. Now that we're 10 to 20 years away from advanced nuclear power designs like molten salt reactors, we will be able to build nuclear to be ultra-safe, and cheap. In the meantime, we have very safe Gen III+ designs such as the Westinghouse AP1000.