David Mackay: A reality check on renewables

How much land mass would renewables need to power a nation like the UK? An entire country's worth. In this pragmatic talk, David MacKay tours the basic mathematics that show worrying limitations on our sustainable energy options and explains why we should pursue them anyway. (Filmed at TEDxWarwick.)

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[canadiannuclearman]

Let’s say you wish to replace a 1Gw nuclear plant with wind power. Let go through the numbers.
Many French reactors have a power level higher like 1.6Gw = 1600 mega watts. We’ll use 1Gw = 1000Mw to keep our arithmetic easy.
A 1 Gw nuclear Plant has a capacity factor or 95% some are higher some lower.
Wind Power has a capacity factor of 33% this can very as low as 25% or a bit higher.
For the layperson this may not seem so important so please bear with me. Because we wish to replace a nuclear plant with a wind farm
To build a wind farm you will need 1Gw/ 33% = 3Gw of power because of the capacity factor. The wind blows 33% of the time. That means 3Gw of power is needed to be produced power so to replace 1Gw of Nuclear. How this is done is wind supplied 1Gw of power to the grid while the remaining 2Gw of power goes to storage. So lets say we have very very predictable power where every third day the wind is blowing and at sufficient speed >20km/hr. So Monday it blows Tuesday and Wednesday the wind doesn’t blow. So on the Monday 1Gw goes to the grid 2Gw goes to storage to be used on Tuesday and Wednesday. Then by some miracle the wind blows on Thursday and the cycle continues… For EVER. If there is no wind power on the third day your out of luck. Now lets calculate the size of the battery. Energy is = power times a unit of time.
1 Joule of energy = 1 watt for one second. Therefore 2, 000, 000, 000 watts (2Gw) needed to be stored in one day or 24x60x60 seconds= 86’400 seconds. So the storage that’s needed is 2, 000, 000, 000x 86, 400=
172, 800Gj of energy or 172, 800, 000, 000, 000 Joules of energy storage. But the kicker here is assuming 100% storage capacity efficiency. Now lets calculate the cost of 3Gw Wind plus 172, 800GJ of energy storage.
Wind’s cost is about $1000 per Kw or $1 per watt. So 3Gw of wind will be $3 billion.
Batteries are about $500 / Kwh or $500 / 3.6 million joules. Or .0001388889 $/J
Therefore 172, 800 Gj x .00013888$/J= $24 billion
So that’s 24 plus 3 = $27 billion to replace 1 nuclear plant. So the cost of storage is the kicker.
But for how long?? A nuclear plant can go for 40 to 60 years.
For a wind farm its life could be 20years. So look to spend 3 $billion times 60/20 (or $9 billion) to cover replacement over 60 years. For batteries lithium ion type they can take 300 to 500 charges. For calculation lets use the generous 500 charges. If the batteries will be charged once every 3 days that’s 1500 days of life.
1500/365= 4.2 years Therefore over 60 years the replacement is 60/4.2= 14 times
So the total cost over 60 years is $24 billion x 14 for batteries plus $9 billion for wind turbines equaling a grand total over 60 years to be 24×14+9=

$345 billion. Over 60 years.

Now do the same for solar but it has a capacity factor of 20% less in Germany.
1/20% =5Gw etc etc. Create your own spread sheet and adjust some numbers if you like.
For nuclear it is 95% Do the math for it as well. You will need 0.05Gw of storage but this could be made up with natural gas. A lot of nuclear power plants have 2 reactors. Darlington 4 Pickering 8. As you can see by the back of napkine calculation it’s the cost of storage. There is a line in the PDF that your can down load from www.roadmaptonowhere.com that I will always remember.

“Fuel is Storage” Wind and Solar are fuel free systems.

But lets look on the bright side Elon Musk can sell us the battery storage for 172, 800 Billion Joules of energy at 100% efficiency. Wow time to buy Tesla stock.

[johnperry]

He was a nice guy, and an excellent physicist. Used to see him around at Cambridge, when I was there. He was skeptical, but sincere. I wonder sometimes what he might think about the progress that has been made in the last few years. He passed away in 2016.

[skaruts]

I just want to point out that lifestyle changes are not simple substitutions or removal of unnecessary habits. Taking a train somewhere is by no means equivalent to driving a car there, as I've seen some people implying. In some situations when the train is a better option people actually use it. But in many circumstances it's not. For example, I worked in a place in Lisbon, Portugal, called Alvalade, where I could get there by car in about 40-50 minutes (including finding a place to park). By train, that involved a 20 minute car or bus ride to the train station, a 30-45 minute train ride to the city, and two subway rides of slightly over 1 hour to the place I worked at. Add up also the waiting and walking times, and I took well over two hours to get there, and the same to get back home. That meant about 4.5 hours, which was more than half of my free time, was wasted on transportation.

Many people are in variations of this situation, or many other situations that are not trivially changed, or not at all. Changing lifestyles is not really a feasible option.

[anaandjorge]

I see in the comments some questions on why he says things of of date... Because the speech is of 2010-2012, not now. There was no Tesla battery. The physics and challenges are right, but the fast increase in efficiency of renewables has been faster than expected, but the problem is still the scale of needs and the need to balance the network, needing a certain level of overcapacity all the time. The network stability is the real challenge, but yes, the technology is moving also into unexpected ways of addressing energy. Transport is the new challenge, even if it goes electrical the needs on the network will be large, Adding demand.

[HeWhoEatsCereal]

Solar energy isn't extremely effective in cloudy UK? Who would have guessed. The speaker uses the UK as an example of why renewables aren't super promising yet if you looked at other regions beyond the cloudy island of England you would find renewables can be and are a viable sources of energy.

[reachforacreech]

it will take a subtraction of consumption and a greater efficiency of products in order for renewable to work in a good time frame.

[ianprado]

It's funny that nuclear is the best energy source JUST from the energy security it provides a nation. But nuclear is also the most profitable, the cleanest, the most versatile, and the safest.

[Ayyoubal]

I hate how he didn't even mention Tesla.

[mikeharrington]

Which special interests donors funded his negative presentation ?