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The Future of Energy: Why Power Density Matters

The Energy Transition

This is the first column in The Energy Transition series by Robert Wilson. This series, exclusive to theenergycollective.com, will take a critical look at the prospects of a transition away from fossil fuels, and promises to abide by the advice of Richard Feynman that reality must take precedence over public relations.

Hong Kong Wind Farm Wakes

The twenty first century will almost certainly witness a transition to an overwhelming urban human population, and hopefully a transition to a low carbon energy system. The former however will have a significant impact on the latter, because a fundamentally urban species cannot be powered locally.

The  continued, and essentially unabated, accumulation of carbon dioxide in the atmosphere may at times make considerations of the requirements of a de-carbonised energy system appear somewhat self indulgent, but I must ask the reader to indulge me, and at a little length.

What would a low carbon energy system look like? (And let’s avoid such fanciful ideas as “zero carbon,” because that would be truly self indulgent.) In essence we would get as much electricity as possible from some combination of renewable and nuclear energy, and electrify as many aspects of our energy systems as is feasible. Predicting the relative composition of such a system is a largely fruitless exercise. However, we can say something about the extent to which it a low carbon energy system will be distributed and “local”. This confidence comes from the difference between the high physical concentrate of energy use in cities, and the relatively low physical concentration of renewable energy resources.

Power density

There are fundamental physical limits to how much energy we can extract from renewable resources for a given area of land. If we want to rigorously quantify this we calculate an energy source’s power density in watts per square metre (W/m2 ).

To get an understanding of this concept consider the recently opened London Array wind farm to the south of England.This is the world’s largest offshore wind farm and according to its owners will generate “enough energy to power nearly half a million homes.” Its total capacity is 630 MW covering a total of 100 km2, and is expected to have a capacity factor of 39%. In other words the power density of the London Array will be 2.5 W/m2. This number is also very similar to the average calculated by David MacKay for existing UK wind farms. The United Kingdom is windier than a lot of the world, and some research suggests that large extraction wind farms will reduce average power density closer to 1 W/m2, so 2-3 W/m2 can be viewed as an upper limit on the power density of large scale wind power. This power density reflects average output, however peak power density of wind farms will be perhaps three times higher, and minimum power density will be close to zero. And it should be noted that it excludes the requirements for manufacturing steel required for turbine towers and the extraction of fossil fuels for conversion to plastics for wind turbine blades. However inclusion of these factors is not likely to result in a significant reduction to power density estimates.

Globally solar radiation available for conversion to electricity averages 170 W/m2, and in sunnier locations it can reach above 200 W/m2. This solar energy however is currently not converted at anywhere close to 100% efficiency. Commercial solar photovoltaic panels typically average between 10 and 15% efficiency. Power density of solar installations must also account for space between panels, either for servicing in solar farms or for spacing between houses in rooftop solar installation. As a result the highest power density achieved is around 20 W/m2 in desert solar PV farms, whereas solar farms in Germany generally achieve 5 W/m2. Future improvements in panel production will hopefully see significant improvements in panel efficiency. However there will remain a firm physical upper limit of 200 W/m2, which will be significantly lower when only considering large scale deployment of residential rooftop solar, due to obvious physical restrictions on panel placement.

At their best biofuels might be able to produce close to 2 W/m2. However power densities of 0.5 W/m2 and below are more typical, with prominent examples of this being corn ethanol for transport and the burning wood for electricity. We will see later that this is a very important consideration for the scalability and sustainability of biofuels.

In contrast typical generation of fossil fuel and nuclear electricity has a power density of at least an order of magnitude greater than that of renewable energy. Power densities are comfortably above 100 W/m2 after accounting for mining etc. And conventional power plants often have power densites in excess of 1000 W/m2. A simple example of this higher power density is this small propane powered generator, providing in excess of 1000 W/m2. This is far in excess of the power density of any conceivable new method of generating renewable energy.  

propane

Why power density matters

A simple thought experiment can demonstrate why power density needs to be a fundamental consideration when evaluating renewable energy. Here it is: Imagine a world where all energy comes from bio-energy. What would be the requirements?

Currently the planet consumes energy at a rate of over 16 TW (16 trillion watts). If we include non-commercial biomass energy used in Africa and Asia, an uncertain figure, this number would increase. However for simplicity I will ignore non-commercial sources and will round our figure down to 15 TW. If we got all energy from corn ethanol we would need to convert a total of 75 million km2 to corn ethanol plantations. This is roughly half of the land surface of the entire planet, land which is somehat scarce. So this simple thought experiment shows there very real limits on how much energy we can, and should, get from biofuels. If we want large scale biofuels to become truly sustainable, a questionable prospect, we will need to see significant improvements to their power density, perhaps improvements of at least an order of magnitude.

Physical concentration of energy consumption

How much energy do we consume per unit of land? For ease of comparison this figure again can be calculated in W/m2. On a global level this is 0.1 W/m2, if we only consider land surface area. Global averages however are not very instructive, power density averaged at the scale of countries and cities is much more important. David MacKay has visualised this much better than I can in his “Map of the World.” Here is the average rate at which countries consume energy, in W/m2, compared with the power density of different renewables: Ideally a country wants to have lots of available land for renewable energy, i.e. they want to be in the bottom left of this graph. Being in the top right however may lead to some problems.

Consider first the United Kingdom and Germany. Both use energy at a rate of just over 1 W/m2. So a back of the envelope calculation will tell you that getting all of their energy needs from onshore wind will require covering half of the UK or Germany in wind turbines. If you have ever been confused by why these countries are building wind farms in the North Sea, instead of on land where it is much cheaper, now you know why. Wind energy’s low power density means you need to put it in a lot of back yards. And there are not as many of them in the North Sea.

Things are even worse in Japan and South Korea. If you covered all of South Korea in wind turbines they would generate less energy than is consumed there. Japan has a similar problem. And this ignores another difficulty: trees. Both Japan (68%) and South Korea (63%) have very high forest cover. If we ignore forested land (which should be out of bounds for large scale renewable energy generation, unless large scale biomass plantations are deemed acceptable) energy is used with a power density of almost 6 W/m2 in Japan and 7.5 W/m2 in South Korea. This calculation makes it clear that these countries can only be predominantly powered by renewable energy through the large scale utilisation of the more power dense solar energy. And social and political constraints may mean this can only happen if the efficiency of typical solar panels increases significantly from their current 10-15%.

Local Energy Is Not A Solution

Some environmentalists and renewable energy advocates have an ideological preference for small and community scale renewable energy. However what if your community looks like this: missingTokyo skyline

Some people may like the idea of running Tokyo on local renewable energy. They will have some difficulty actually doing it, and that’s putting it mildly.

Since 2008 the majority of humanity live in cities. And by 2050 it is probable that we will see seventy or eight percent of humanity living in cities. The key energy challenge this century will be providing energy for these cities, and quite clearly local distributed energy is not a solution. To see why this is the case requires untangling some issues.

Here are some considerations. An average North American has an annual energy consumption of just over 7 tonnes of oil equivalent (toe)., which is the equivalent of a rate of 9,000 watts. However, this is almost double what it is in countries such as Germany, France and Japan. A comparison of these countries in terms of key well being measures makes one thing clear: there is no evidence that North Americans have greater well being as a result of their excessive energy use. Americans don’t live longer, aren’t healthier, or better educated than countries that consume half as much energy per capita. That this high per capita energy consumption comes with a very significant environmental cost – global carbon dioxide emissions would drop by almost 10% if North Americans consumed like Europeans – but little gain in terms of human well being, suggests that is is not desirable for other countries to emulate North American consumption patterns.

Further evidence for the desirability to limit, and probably reduce, per capita energy consumption in modernised countries is given by its evolution in recent decades. Instead of increasing in the long term, per capita energy consumption now appears to have peaked in almost all modernised countries. Here are some examples:

Per capita consumption has declined steadily in the United Kingdom for the last decade and is now at its lowest point for over four decades:

United Kingdom

The United States saw peak per capita consumption in the 1970s, with consumption now seeing an apparent decline. And the fact that per capita consumption did not rise in the age of the Hummer suggests significant room for movement.

US

Germany is also now seeing declines in per capita consumption.

Germany

In Japan per capita consumption appears to have peaked in the late nineties and is now in decline:

Japan

So, many modernised countries are now seeing reductions in per capita energy consumption, and this is not being accompanied by a reduction in quality of living. Any sensible long term energy and climate policy should include a strong desire to continue this trend. The belief that the world can transition to both American levels of energy consumption and to a low carbon energy system by the middle of this century ignores the vital lessons of previous energy transitions, and given the current position of renewable and nuclear energy it appears delusional. The world therefore must be much more like Japan than America.

And cities must play a key role in reducing energy consumption. The most important and effective way to do this is simple: make them dense. For a full elucidation of why, I recommend books by Edward Glaeser and David Owen. But the key reasons are easy to understand: a dense city lets you walk or take public transport instead of drive and it lets you live in a more energy efficient apartment building instead of a large inefficient house. Packing people more tightly together in cities may not be to the taste of everyone, but it appears to be one of the most achievable and practical ways to reduce how much energy people consume.

Let us now move forward to 2050, and the world is as I hope it will be. Global population will have peaked below 9 billion as a result of the spread of the demographic transition to modernising countries, and the success in reducing infant mortality and widespread availability of contraception. Perhaps 7 billion of us will live in cities, and they will consume much more like modern day Japanese than Americans.

How will we provide energy for these cities? The answer appears to be large, centralised power plants, whether they are wind, solar or nuclear. Here I assume, wishfully, that we have managed to get rid of fossil fuels, an unlikely prospect. The answer however is almost certainly not local distributed energy, and for simple reasons.

Consider Manhattan, not what many would typically look at as the green ideal. Yet here you will find significantly lower per capita energy consumption than in almost every American city. You will also find energy consumption far greater than can conceivably be provided by local renewables. A recent study managed to map energy consumption in the city that never sleeps right down to the individual city block. This is what it looks like:

A typical block in Manhattan consumes energy at a rate of over 1,000 kWh per square metre each year, a power density of over 100 W/m2. This is almost two orders of magnitude greater than the power density of wind power, and obviously you could not plaster Manhattan in wind turbines. Solar power is not much better. Imagine that we could cover 20% of Manhattan in solar panels. This would give us no better than 5 W/m2. Clearly Manhattan is not getting its energy locally. And as you can see from the above map the other boroughs of New York are not going to fare much better.

How about the rest of North America? If we reduced per capita energy consumption to Japanese levels, a sensible but unpopular idea, could many American cities run largely on local renewables? The graph below shows population density versus energy use density in this lower consumption America: usDensity

Low density Phoenix perhaps has a shot at getting most of its energy from solar power. Covering 25% of Phoenix in solar panels would produce as much energy as is consumed in Phoenix. The practicality of this is of course rather questionable, and getting more than 50% of Phoenix’s energy from local solar will require something that currently does not exist: a cheap way to store energy on a large scale. A system involving more than 50% of energy coming from solar will thus inevitably require the accounting of land requirements for large scale storage, an uncertain prospect, and significant losses of solar panel output due to efficiency losses during storage and curtailment of excess.

The prospects of American cities running largely on local renewables thus seems unlikely, and 83% of Americans live in cities.

A global appraisal

The world’s two hundred largest urban areas are home to over 1.2 billion people, and a quarter of these areas are more densely populated than New York (10,000 people per square kilometre). This is shown below: PopDensity

Before asking if these cities can run on local renewables I must first mention the too real disparities in global energy consumption. Below is a comparison of the population of countries with their per capita energy consumption, with population plotted on a logarithmic scale due to China and India being much larger than other countries. And I include lines showing typical European and North American per capita energy consumption. GlobalEnergyComp

While there are about 350 million North Americans who can, and should, reduce their energy consumption to European levels, there are even more at the bottom who must increase their energy consumption significantly to improve their quality of life. Quantitative comparisons are sobering. Over 35 countries have per capita consumption at less than 10% of North American levels, with populations totalling over 2 billion. Despite the apparent desires of some environmental NGOs (for an example see page 11 of this WWF report) it is therefore undesirable to propose reductions in global energy consumption. The modernised world may consume excessive energy, but energy consumption is much too low in modernising countries to let us decrease global energy consumption without negative humanitarian impacts.

We therefore should have a desire to both reduce excessive consumption in modernised countries and increase energy consumption in modernising countries. I am not going to suggest a prescriptive end point. Instead I will assume that consumption levels in modern day Japan can provide a very good quality of life, and exceeding these levels is unnecessary.

If the populations of the world’s 200 largest cities consumed energy like modern day Japanese energy use density would look like this:

PowerDensityofCities

In total 10 cities would have power density greater than 100 W/m2, 56 would have power density greater than 50 W/m2, while 181 would have power density of over 10 W/m2. That is 90% of the planet’s 200 largest cities almost certainly cannot be powered predominantly by local renewable energy. The population densities of these cities are not significantly different than the rest of the world’s cities, so we can conclude that the the vast majority of cities cannot be powered by local renewables. And this suggests very serious limits to the role of local distributed energy in a world where more than 70% of us will probably live in cities.

The prospects are even worse in individual countries. Of the world’s 200 largest urban areas, 17 are in India. Below I have isolated these cities.

India power density

120 million people live in these cities. Covering any of them entirely in 10% efficient solar panels will generate less than half of their energy needs. And look at that dot in the top right, that is Bombay. For Bombay to get all of its energy needs from solar in my hypothetical future it would need to harness almost 100% of the solar radiation that strikes it, a remote prospect. This extremely high population density is routinely ignored by western environmentalists calling for distributed energy to be the solution to India’s energy problems. It quite clearly is not.

In this century the bulk of humanity will live in large densely populated cities. If the citizens of of these cities are to attain a high quality of life they will require large centralised energy generation. This is not a matter of ideological preference, but of engineering reality.

Robert Wilson's picture

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Discussions

Robert Wilson's picture
Robert Wilson on Aug 16, 2013 10:59 am GMT

Warren

The question here is not stupid. My post was about the land requirements for renewable energy. Surely an expert on biogas can tell me the requirements for replacing 78 billion cubic metres of gas with biogas. This should be a relatively easy thing to do.

After all you told me in your initial reply that biogas produced 3-5 times more energy per unit of land than liquid biofuels. A rough estimate of land requirements should be easy to calculate.

Robert

Warren Weisman's picture
Warren Weisman on Aug 16, 2013 11:10 am GMT

Apples and oranges, bro. You’re talking about a centralized fossil fuel grid that wastes 3/4 of its energy through heat loss and resistantce. No renewable energy can replace such a ridiculous, wasteful system. It CAN, however, replace distributed, sane energy requirements to meet a specific need.

You’re also not taking into consideration the energy wasted with 80’s-era secondary clarification and activated sludge wastewater treatments, liabilities that would be turned into assets with well-planned biogas co-generation wastewater plants as most in Sweden are now.

Nor are you taking into consideration the nitrogen that biogas slurry offset in local agriculture, which otherwise has to be extracted out of the atmosphere with fossil natural gas using Haber-Bosch process.

Like I said, you don’t know the first thing about the process, you’re just out to prove a conclusion you have already drawn.

Robert Wilson's picture
Robert Wilson on Aug 16, 2013 12:14 pm GMT

Warren

This is a rather unpersuasive sales pitch. Do you have something to say about the power density of biogas or not?

Robert "Bob" Mitchell's picture
Robert "Bob" Mitchell on Aug 16, 2013 2:51 pm GMT

Mr. Weisman:  While there is definate room for improvement in our electrical grid and I am a strong proponent of upgrading and beefing up of the grid, I’m not sure that your “a centralized fossil fuel grid that wastes 3/4 of its energy through heat loss and resistantce” statement is accurate??

The general consensus of transmission losts over the grid is in the 6 – 8% range.  Were you factoring in the efficiency of the power generation itself?

 

Bob “The Clean Energy Guy” Mitchell

 

Robert Bernal's picture
Robert Bernal on Aug 16, 2013 5:09 pm GMT

On the global scale, rooftop will NOT provide all our energy, but there is much room for improvement, as long as most of the money needed to develop the global low carbon solutions are not wasted on them.

The weight of a solar panel per unit of area is nothing compared to the weight of the roof itself. Consider that the max rated roofing load is considerably more than just the weight of the roof alone. If in snow area, then it must be built to be rated for much higher. I would search these, but I already know that the actual weight vs construction industry standards is not already close to “max rated”.

Solyndria is not really a good example for anything except for gov’t waste! China’s prices were already lower than theirs at the time and it was also obvious that Chinese companies were buying equipment for machine automation to lower their prices even further.

On the global scale, rooftop would still be better than biofuels because its power density is greater.

Warren Weisman's picture
Warren Weisman on Aug 16, 2013 5:54 pm GMT

Yes, Robert. If I take a handful of coal and put it in a boiler to generate electricity, 75% of the BTU’s will be lost as heat.If I take the same handful of coal and burn it in a boiler in my basement, the lower temperature boiler will be less efficient, but the possibility exists to capture some of that waste heat, if it is needed (Although, generally, when the heat is not needed the boiler would generally not be operating). And most importantly of all, unlike massive 2 Million horsepower turbines, the smaller boiler can be shut down for instant fuel savings when not needed.

Robert "Bob" Mitchell's picture
Robert "Bob" Mitchell on Aug 16, 2013 6:18 pm GMT

Mr. Bernal:

As I’ve mentioned in my earlier comments, my belief is that our energy needs can and will eventually be met by a variety of clean solutions, including; solar, wind, title, energy efficiency, as well as a host of other technologies.

This belief is backed up by several feasibility studies such as this report produced by the World Wildlife Fund that states that by 2050 all of the world’s energy needs could be met through renewable energy without conflicting with conservation objectives. http://wwf.panda.org/what_we_do/footprint/climate_carbon_energy/energy_s...

To Mr. Steven’s ascertion that solar rooftop arrays have a problem with weight, I have found nothing to confirm this except in situations where the building is poorly designed or damaged.  Since he wasn’t able or willing to provide me with any information other than his opinion, I’m going to continue to believe that this simply isn’t a major issue in the adopting of renewable energy.

To your ascertion,  “On the global scale, rooftop will NOT provide all our energy”, I agree.  Nor do I think that it will have to!  A 2008 study published by the NREL concluded that about 22% of our total electrical generation needs could be satisfied via roof top installations  (http://www.nrel.gov/docs/fy09osti/44073.pdf) and I’d be happy with that.  That 22% also didn’t count other areas that could be utilized for solar deployment such as parking lots and brownfield areas.

That 22% also didn’t count the reduction in energy demand that could come from solar thermal systems that could be utilized to not only provide for domestic hot water, but also could be utilized to dehumidify air (and reduce airconditioning loads), as well as to provide heat.

As the original article states, this might not be enough to provide for an entire city’s energy needs, but when you combine it with energy efficiency and conservation, it can indeed go a long way towards providing for a city’s energy needs.

 

Bob “The Clean Energy Guy” Mitchell

 

Warren Weisman's picture
Warren Weisman on Aug 16, 2013 6:24 pm GMT

Using the example of an easily accessible feedstock with high gas yield – grass silage – an average yield of, say, 10 tons per acre and a biogas yield of 400 cu.m. per ton, that’s 4,000 cu.m. per acre or approximately 1 cu.m. per sq.m. 35.4 cu.ft. of 60% CH4 biogas at 600 BTU per cu.ft.= 21,240 BTU/m2 or 6,221 watts per m2.

Robert Wilson's picture
Robert Wilson on Aug 16, 2013 6:49 pm GMT

Warren

6,221 watts per square metre. You may want to re-do this calculation.

Average solar insolation is 170 watts per square metre. Photosynthesis is a process that converts solar energy into chemical energy in plants. The conversion of solar energy into chemical energy is always at an efficiency of less than 10%, so 20 watts per square metre is physically the maximum power density you can possibly get.

http://en.wikipedia.org/wiki/Photosynthesis#Efficiency

The only way this feedstock is giving you 6,221 watts per square metre is if the laws of physics do not apply to it.

Warren Weisman's picture
Warren Weisman on Aug 16, 2013 6:57 pm GMT

Ha ha. Gotcha. It defies the laws of physics to grow grass.

Robert Wilson's picture
Robert Wilson on Aug 16, 2013 7:11 pm GMT

Warren

I really hope you don’t have the future of your biogas business relying on this estimate for how much energy you can get from this feedstock, because it will go out of business next Tuesday.

Warren Weisman's picture
Warren Weisman on Aug 16, 2013 7:21 pm GMT

I hate to break the news to you, we use grass silage in multiple biogas digesters every day.

 

Clayton Handleman's picture
Clayton Handleman on Aug 16, 2013 7:44 pm GMT

I think you divided by an hour rather than a year.

I assume your 10 ton number is 10 tons / year.

Based upon your numbers your rate of energy production is as follows:

(21240 BTU / m^2) x (1055 Joules / BTU) = energy per meter squared per YEAR.

to get watts divide by seconds per year and the result is just under a Watt as average power production per square meter over an entire year.

 

It sounds like you have an interesting approach to energy renewable energy and likely valuable.  However your snotty tone towards the author of the thread is unfortunate, not funny and serves to undermine respect for you.  While some aspects of this thread have been passionate, it has for the most part remained respectful, hope you will take note in future comments.

 

 

 

Warren Weisman's picture
Warren Weisman on Aug 16, 2013 7:48 pm GMT

With just myself and 2 other people on Hestia Home Biogas board we have 40+ municipal and farm scale biogas projects (>1 ton/day), mostly in the 10-30 ton/day range, including a distillery waste digester in India that produces 600 tons per day into over 1 Million cubic feet of biogas per day.

 

George Stevens's picture
George Stevens on Aug 16, 2013 8:39 pm GMT

A credible alternative to the cost of natural gas carbon emission? Well it is quite hard to put a number on due to the significant margin of error in the best climate models available specifically in regards to the correlation of temperature rise and CO2. Im not saying we should do nothing, but the number that was provided is completely arbitrary when it comes to natural gas emissions because the magnitude of its negative implications is hazy, and using it as an energy source provides a tremendous economic benefit and frankly cheap energy does tremendous good for the human condition.

 

If you want to compare land disturbance of wind/solar vs natural gas you have to consider the transmission and the mining required for wind, solar, and batteries per unit energy and then compare that to land disruption of energy dense natural gas. That is an apples to apples comparison.

George Stevens's picture
George Stevens on Aug 16, 2013 8:14 pm GMT

Fukushima clean up efforts are not predicted to cost 100 Billion.

New nuclear plants incorporate passive cooling systems and are incapable of experiencing the same mode of failure as Fukushima.

Your statement above is the opposite of what happens in the real world where the lower the risk, the lower the rate of insurance. The US Nuclear Regulatory Commission has done due diligence on this topic and is a qualified actuary to call for 13bn in insurance per facility.

 

George Stevens's picture
George Stevens on Aug 16, 2013 8:21 pm GMT

Robert,

small modular reactors are a bit different than the nuclear you are envisioning, I think you should check out the Mpower and nuscale designs and you may think a bit differently on this topic.

Obviously SMRs are smaller

They are also built below grade

and in designs such as Nuscale’s the reactor is completely submerged in a water pool and the chance of a meltdown is virtually non-existent.

These designs also allow for refueling to only occur once every few years.

Urban fossil generation plants often take up 40 acres or more and I believe Mpower is projecting a 40 acre exclusion zone.

So I understand putting a nuclear plant in a city ‘sounds’ crazy, but in reality no its really not crazy at all.

George Stevens's picture
George Stevens on Aug 16, 2013 8:37 pm GMT

Guess you didn’t look very hard:

http://www.solarindustrymag.com/issues/SI1301/FEAT_01_Commercial_PV.html

http://green.tmcnet.com/topics/green/articles/2013/06/28/343972-solarcit...

 
“The SunPower T5 Solar Roof Tile is the most powerful solution for
area- or weight-constrained flat rooftops”
 
Warren Weisman's picture
Warren Weisman on Aug 16, 2013 8:43 pm GMT

That’s wet weight.

Robert Bernal's picture
Robert Bernal on Aug 16, 2013 11:19 pm GMT

My two cents…

Biogas will NEVER be able to power the world, due to the massive amounts of land it would take to do so. Nevertheless, it is most probably a good thing as long as it is not overly subsidized. Like, if I could convert weeds in my back yard into fuel, that would be awesome.

It would be devastating to waste money on anything that does not have the potential to power a growing world without fossil fuels all by it self.

Warren Weisman's picture
Warren Weisman on Aug 17, 2013 1:05 am GMT

I could genuinely care less if people accept reality or not. My reputation among my peers and our customers is well established. The article is supposed to be about transitioning from fossil energy to renewable energy, yet neglected to mention the best renewable energy source of all. Whoever wants to is more than welcome to research anything I posted.

Warren Weisman's picture
Warren Weisman on Aug 17, 2013 9:42 pm GMT

That sounds about right. 2,453 m3 per acre.

It’s important to note, however, the fertilizer replacement value (FRV) of biogas slurry – the liquid byproduct of the biogas process – is far more valuable than anything that can be done with the gas. Since nitrogen is the limiting factor of human life on earth and the only other way to get it is extract it out of the atmosphere using fossil natural gas.

The biogas process is also very aggressive against pathogens and parasites – which is why it is used as the first stage in wastewater treatment.

All biomass use has the advantage over fossil fuels of being able to be grown locally and eliminate extensive transmission and transportation energy expenses – which it doesn’t seem these “energy density” calculations take into consideration, even though transmission lines cost a Lamborghini sports car per mile.

In addition to the advantages of localized prodcution, biogas has these additional advantages over not just direct burning of biomass, but all other energy sources.

donough shanahan's picture
donough shanahan on Aug 19, 2013 3:01 pm GMT

Another way of looking at this

The UK produces around 100 million tonnes of waste that could be used to generate biogas. Assuming that this waste has no free water (but still has water in its structure), this could yield about 7% of the UK’s natural gas usage if we also assume it was grass based. Assuming it is slurry based would achieve a much lower return. I am not sure how much room there is in the UK for additional agriculture.

http://www.biogas-info.co.uk/index.php/biogas-yields-agri.html

donough shanahan's picture
donough shanahan on Aug 19, 2013 3:05 pm GMT

In reply to a recent Guardian article on the issue I said the following

According to the article above we have about 100m tons of waste that could be used. Now ignoring that all of this waste could not be turned into gas and taking a high yield for biogas from this waste (200m3 per tonne) and noting the the annual UK consumption of natural gas is approx 90 billion m3, we have the potential to produce 22% of the UK’s gas usage.

Now to that pesky amount of water. Meat typically contains 70% water and fat is the same. Fruits are around 80% and vegetables are typically 90%. Taking the lower range, that 22% turns into around 7% using a generous calculation.

Robert "Bob" Mitchell's picture
Robert "Bob" Mitchell on Aug 19, 2013 5:56 pm GMT

Mr. Stevens:  That’s not completely true!  Each nuclear facility is only required to have $375 million in liability coverage.  If an accident occurs that causes more damage than that, each of the approximately 104 (I’m not sure about that number with a couple of plants being shuttered), plants being required to pony up about $111.9 million each to cover the excess damage.

If more than 15% of this pool is used, then the matter goes to federal court to prioritize payments.  If the damages go beyond this pool’s ability to pay and not become insolvent, then it goes back to Congress and we the tax payer’s will be on the hook.

Also, the insurance isn’t comprehensive in that waste, either stored or in transit isn’t always covered, nor is damage to the plant itself (which in theory will have been paid for by the rate payers) In addition, claims haven’t always been dealt with quickly.  Many of those affected by Three Mile Island had to sue to be made whole and some of these suits weren’t completely settled until as late as 2003!  http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/funds-fs.html

There are also other issues to consider in regards to this “insurance”.  One that hits close to home (approximately 11 miles from my own home) is that the insurance coverage is only based upon a 10 mile evacuation zone.  Which considering that the US government itself recommended a 50 mile evacuation zone for the recent fukushima disaster, doesn’t make me feel all that comfortable!  The fact that Japan itself (even after raising it’s allowable radioactive exposure limit to 20 times what the US allows) declared areas within 12 miles to be inhabitable to humans, kind of worries me a bit??? (and that doesn’t count the 80 square miles northwest of the plant and beyond the 12 mile permanant exclusion zone).

So, even after raising it’s “acceptable” limit there is still an area of approximately 4500 square miles (about the same size as the state of Connecticut) that exceeds this limit.  How would you like to try and sell your home with THAT feature? 

But even if you say, “Screw you” to all of those people who live outside of the excusion zones, just the value of the land, businesses, and homes of those inside of the excusion zones has a estimated value of between 250 billion and 500 billion dollars…far exceeding even the 13 billion dollars of liability coverage that US plants now have.

BUT!!! It doesn’t stop there!  40 miles of fisheries off of the Fukushima coast was forced closed and an untold amount of sea life was contaminated and I doubt if anybody cuts those poor creatures a check!

Add that to the misery of over 159,000 people who were evicted from the excusion zones…

WAIT!  There’s More!  If you order your nuclear power plant today, we’ll include an extra 200 miles of contamination of food stuffs and water!  And if you act now, we’ll even throw in biomagnefication so that the benefits of nuclear power can be enjoyed on up the food chain!

The sad thing is that I could go on…and on and on….which goes to show that you are wrong; the nuclear industry is not properly insured even with the backing of the US government.

 

Bob “The Clean Energy Guy” Mitchell

 

 

Robert "Bob" Mitchell's picture
Robert "Bob" Mitchell on Aug 19, 2013 6:10 pm GMT

You’re right!  The cost of cleaning up Fukushima isn’t 100 billion….it’s more than twice that to as much as 5 times that amount according to any number of objective studies.  And that isn’t counting the damage done to areas outside of the 12 mile excusion zone (and 80 square mile excusion zone northwest of the plant, but beyond the 12 miles).  Nor the damage done by radiation that travelled world wide and is estimated to kill about 130 people https://energy.stanford.edu/news/mark-jacobsons-lab-calculates-health-co...

One other point that I would like to make to those who think that it could happen there, but not here….there are currently 23 nuclear plants operating here in the US that are of similar design to the fukushima plant!  Also, since only about 19% of the radiation from this disaster fell on land, a similar disaster here could be much worse!

 

Bob “The Clean Energy Guy” Mitchell

 

 

Clayton Handleman's picture
Clayton Handleman on Aug 19, 2013 6:12 pm GMT

Fabulous comment! 

Please consider taking a little time to add links to back it up and then submit as a post on externalities rather than a less visible comment in a played out thread.

 

Clayton Handleman's picture
Clayton Handleman on Aug 19, 2013 6:44 pm GMT

I completely agree with you.  The lower the risk the lower the cost to insure.  So I am confused as to why you wouldn’t be in favor of the nuclear industry covering all plausible accidents.  Just as the cost of my umbrella drops as I get catestrophic damage coverage, wouldn’t it be the same here?  So why do you support the taxpayer being insurer of last resort instead of just having the whole thing insured by the utilities with the nuclear plants?  And BTW, why aren’t nuclear power plants insured by private companies rather than self insuring or going to a private insurer?  After all, wouldn’t you think they would be clamoring for this no risk, high premium opportunity?   

You suggest that none of our power plants would EVER have an accident because they are not like the Fukushima plant.  Well what credible sources anticipated what happened at Fukushima? 

And as Robert Michell points out, there ARE credible sources calling into question safety at a number of our nuclear power plants.

 

Robert Bernal's picture
Robert Bernal on Aug 19, 2013 10:12 pm GMT

PV, wind, wave, tidal, geothermal and (maybe) biofuels are all good for filling in… but these can not displace 90% of the fossil fuels.

The world has three choices at the global scale: a meltdown proof nuclear (such as MSR), a storable solar (such as CSP) and fossil fueled depletion (and excess CO2’s biosphere alteration, such as what trivial power sources can not prevent). It’s up to us to develop the cheapest with the most potential because our kids deserve to have more energy, not less (and because they need that extra energy to clean up the excess CO2).

George Stevens's picture
George Stevens on Aug 20, 2013 1:59 pm GMT

You could go on and on but it would be pointless until someone educates you in the basics of radiation.

The allowable radiation exposure limit in Japan was moved up to 20 mSv which is about equal to the radiation dosage of getting 2 abdominal CT scans over a three year period. 

Is there any body of research that shows demonstrated health risk in such exposure? I believe not. It is a conservative number to say the least.

The mode of failure at Fukushima was meltdown caused by loss of cooling function the mechanism was simply no electricity. The NRC has gone to extreme lengths to see that the same failure will not occur with reactors in the US, and all newly built reactors avoid this problem by design with passive cooling functions. 

So given the operating history of the US nuclear fleet and some actual knowledge about how reactors work along with the risks of radiation exposure, I think the current insurance policy is adequate.

George Stevens's picture
George Stevens on Aug 20, 2013 2:06 pm GMT

What I said was: “New nuclear plants incorporate passive cooling systems and are incapable of experiencing the same mode of failure as Fukushima”

Existent plants still require electricity for cooling functions. Most of these rely on batteries in the event of grid failure. The NRC modified requirements in the light of Fukushima so that extreme precaution is now taken in the maintenance of back-up power systems. 

George Stevens's picture
George Stevens on Aug 20, 2013 2:23 pm GMT

First estimates included costs as high as 13 billion $ (1 trillion yen), as cited by the Japanese Prime Minister at the time, Yoshihiko Yoda 野田 佳彦. However, this estimate was made before the scope of the problem was known. It seems that the contamination was less than feared. No strontium is detectable in the soil,[1] and though the crops of the year of the disaster were contaminated, the crops produced by the area now are safe for human consumption.[2]

A World Health Organization study on the matter reported that future contractions of cancer and deaths attributable to Fukushima radiation exposure will be undetectable compared to norms.

It is good to be extremely cautionary about nuclear power, but it seems that you and Clayton are making assertions without basic understanding of how these reactors work, how they can potentially fail, and what is the actual risk in the event of such radiation exposure. 



George Stevens's picture
George Stevens on Aug 20, 2013 3:20 pm GMT

Thomas, you are claiming that this sole wind-farm is performing better than average due to technological advancements in the turbines themselves, rather than above average wind resource at this particular site, correct?

Care to substantiate that claim with details of the specific turbines used and how they are superior to past turbines?

In most cases I am finding that wind turbines operate in the field with a lower capacity factor than was projected. Case in point being Germany’s fleet of wind turbines that have achieved a quite miserable capacity factor of 17%.

Also the effects of shadowing cannot be neglected when we consider scaling wind energy up: http://www.seas.harvard.edu/news/2013/02/rethinking-wind-power

George Stevens's picture
George Stevens on Aug 20, 2013 3:27 pm GMT

Guess you didn’t look very hard:

http://www.solarindustrymag.com/issues/SI1301/FEAT_01_Commercial_PV.html

http://green.tmcnet.com/topics/green/articles/2013/06/28/343972-solarcit...

 “The SunPower T5 Solar Roof Tile is the most powerful solution forarea- or weight-constrained flat rooftops”

Clayton Handleman's picture
Clayton Handleman on Aug 20, 2013 4:36 pm GMT

Below is the comment that I originally replied to.

I am not sure if you don’t understand my question or if you are just being evasive. 

My point is that having the taxpayers insure the nuclear industry is an externality that should be monetized.  It is that simple. 

I think that what I am understanding you to say is that for the catastrophic umbrella that is fine with you. 

 

You make a second point which is that the new reactors are inherantly safe.  They are safer, but both TMI and Fukushima were supposedly safe.  And in 20-20 hindsight people are saying yeah but its different now.  When TMI happened I was an undergraduate.  The officials were saying that it was a complete suprise and they could never have predicted it.  A nuclear engineering student on my dorm floor pulled out a high school composition that he had written prior to TMI which described exactly the accident that we saw.

It is also worth pointing out that my high school composition was on nuclear power and I recall that the promise at that time was that the nuclear waste problem would be solved by the turn of the millenium.  It has not been.

So at the end of the day, justified or not, the nuclear industry has a huge deficit in public trust.  The technical issues are too difficult to convey to the general public so they are left trusting the experts.  The industry is percieved as having cried wolf once too often.  Probably the nuclear industry’s most difficult problem to solve will not be technical but rather it will be regaining the public trust.  I think that, barring a catastrophic event such as the shut-down of the gulf stream, the nuclear industry has no more than a decade to get their house in order on multiple fronts: regaining the public trust, agreeing on and bringing online new low risk reactor technology, resolution of the waste disposal problem and adequately addressing terrorist vulnerability. 

Good luck with that!   ; )

And with headlines like this, you have your work cut out for you! – http://www.reuters.com/article/2013/08/20/japan-fukushima-leak-idUSL4N0G...

 

“US nuclear generating facilities are properly insured. The NRC requires just shy of 13bn in coverage be available per facility, and the Price-Anderson act exists to cover the unlikely occurance of claims exceeding the insured amount.”

“It is difficult to think of a scenario where a modern reactor with passive safety systems would have such an incident that would require the full 13bn of mandated coverage.”

Robert "Bob" Mitchell's picture
Robert "Bob" Mitchell on Aug 20, 2013 4:59 pm GMT

George:  You asked for it, so here goes! 

“The allowable radiation exposure limit in Japan was moved up to 20 mSv which is about equal to the radiation dosage of getting 2 abdominal CT scans over a three year period.”

The problem with that statement is magnitude.  If ONE person has two abdominal cat scans within three years, they raise their risk of developing cancer by a relatively small amount.  However, if you 100,000 people have two cat scans within a three year period, someone is going to die! 

Actually, it’s worse than that!  Cat scans subject the recipient to about 150 to 1100 times the radiation that they would be exposed to by a conventional xray or about one years worth of exposure from natural sources.  In 2007, that amounted to about an extra 29000 cases of cancer just in the US.  One study estimates that there is an increase of about 1 extra case of cancer for every 400 to 2000 chest cat scans.  Now, times that increase by being exposed to this additional radiation every day for the next couple of hundred years due to the fact that Cesium 137 (which has become inextractably lodged in the soil, plants and water of the area) and that has a 1/2 life of about 30 years…with it taking about 10 one half lifes to completely dissipate and you can see why they’ve declared the area “uninhabitable”.

If they had stuck to their original “safe” limit and the one still held on to by the US and many other countries, the exclusion zone would have had to be extended much further.

http://www.scientificamerican.com/article.cfm?id=how-much-ct-scans-incre...

http://www.psr.org/environment-and-health/environmental-health-policy-in... (This group, Physicians for Social Responsibility, won the 1985 Nobel Peace Prize)

Regarding the reasons that Fukushima failed, does it really matter?  Loss of electricity here, a stuck valve there, leaky pipes on this one or a fire at that one.  When the next nuclear disaster happens, it could be one of these reasons or one of a thousand other ones that we haven’t considered…such as where to place your back up cooling generators in the event of a Tsunami… The fact of the matter is that there is indeed a failure rate!  And while this rate might be small, the results of a failure can be catastrophic! 

Also George, if we build out all of these new nuclear plants that you apparently want, where is the fuel going to come from?  While I’m open to considering Thorium realtors, they apparently aren’t quite ready for prime time yet and nobody really knows when and if they ever will be!  So, as of right now, based upon current usage, we have about an 80 year supply that is economically recoverable.

Double the number of reactors and that number will drop to 40 years…seems like a long time unless you’re a Cub’s fan?? (which for some reason I think that many proponents of nuclear power as being our energy savior seems likely to be the case).

So no, barring a major game changing development, I don’t see nuclear as being that savior.  A band aid for right now, but long term I really don’t see an alternative to renewable energy…even if you’re willing to insure the world based upon your misguilded opinion.

 

Bob “The Clean Energy Guy” Mitchell

 

 

Clayton Handleman's picture
Clayton Handleman on Aug 20, 2013 8:18 pm GMT

Got it.  So from the perspective of logical consistency you just killed your own arguement.

 

You have said that there is no risk beyond the current $13B because are good at what they do and they came up with the right number.

But didn’t those actuaries arrive at that number prior to Fukushima and before the NRC modified the requirements to address loss of power?   

So the way I see it is that there are two possibilities here:

Case 1) Prior to Fukushima the loss of power scenario was considered to be sufficiently addressed by measures in place by both the actuaries and the NRC.  And at that time the actuaries set the insurance cap at $13B – Then came Fukushima and the NRC required upgrades to the fleet of plants.  But the $13B has remained.  Keeping it the same after eliminating risk means that it was too low before the risk was eliminated.

Case 2) The loss of power assumption was not considered.  This would mean that there was a failure mode that was unknown at the time.  And if we now know that the experts are making occasional bad calls then the risk is higher than previously thought. In that case the $13B is too low now.

 

 I do not have to be a nuclear power plant expert to conclude, using basic logic, that the experts were either wrong before Fukushima or after it and the $13B was too low either before, after or both before and after.

 

One way or another the government has been or is subsidizing the externalized risk.  I would like to see the power companies pay rather than the tax payers.

 

 

 

 

 

 

George Stevens's picture
George Stevens on Aug 20, 2013 9:10 pm GMT

Clean Energy Guy, I appreciate your passion for the energy topic, but lets try to look at the issue comprehensively.

You are right there is a demonstratable cancer risk for a CT scan, though it is low, reported at between 1 in 2000 to 1 in 10,000+.  

Before we begin to hyperventilate let’s zoom out and remember the scope of what we are talking about. We are not talking about nuclear plants in general creating this type of cancer risk, we are talking 1 specific circumstance in which a relatively small population will be subjected to radiation exposure that carries an increase in the risk of cancer development that is lower lower than living near a coal plant or having a spouse that smokes. 

Is this still a bad thing? Yes and we should do all that we can to avoid a repeat (new NRC guidelines and new reactor designs). But does it mean that we should abandon nuclear entirely? absolutely not. You might be surprised to learn that including Fukushima and Chernobyl nuclear energy has a lower deaths/kWh rate than even wind and solar PV:

http://www.forbes.com/sites/jamesconca/2012/06/10/energys-deathprint-a-p...

http://www.ecogeek.org/component/content/article/3554-evaluating-energy-...

“Regarding the reasons that Fukushima failed, does it really matter?”

YES! Robert I do not at all intend to be insulting but you like many other nuclear critics seem to completely lack an understanding of reactor design and how new nuclear reactors differ in regards to safety when compared to those constructed decades ago. possible failure modes are well known and were known before these accidents, design can be changed to avoid the possibility of such accidents. There are small modular reactors being developed now that are truly ‘walk away safe’. I urge you to at least look over the following links on modern reactor safety systems and you may come to a different conclusion than you currently hold:

These designs applied or are applying for DOE SMR funding:

http://www.nuscalepower.com/safe.aspx

http://www.kpbs.org/news/2012/may/21/better-nuclear-power-plant/

http://www.generationmpower.com/technology/

Reactors currently being built in the US:

http://www.ap1000.westinghousenuclear.com/ap1000_safety.html

“Also George, if we build out all of these new nuclear plants that you apparently want, where is the fuel going to come from”?

Costs of fuel account for between 5-15% of total generating costs for a given reactor, so uranium could potentially be extracted from more dilute reserves or even extracted from sea-water without necessarily being a detriment to overall costs.

Fast neutron reactor technology is proven and could nearly close the uranium fuel cycle providing enough energy to meet global demand for many centuries. 2 such reactors are applying for US DOE SMR funding (General Atomics EM2 and American Atomics Hope 10) and Russia will build a few of their own within the decade after having committed 31 billion in funding over the next two years to fast reactor development.

Uranium is known to be abundant in the Earth’s crust, history has taught us that when demand for raw materials approaches known reserves extensive exploration efforts are funded and further reserves are inevitably discovered. This has been demonstrated many times with fossil fuels where exploration efforts have been several times greater than for uranium.

“even if you’re willing to insure the world based upon your misguilded opinion”

Bob, Lets not sink to the level of such insults, it undermines the effort of information sharing. You were right about the CT scan cancer risk, in light of the information provided above you might be a big enough man to perhaps acknowledge that you may not have been adequately informed about many aspects about nuclear technology including potential safety and the issues regarding available fuel..




Bas Gresnigt's picture
Bas Gresnigt on Dec 24, 2013 2:04 pm GMT

Renewable score superior compared to mPower or any nuclear power plant.
Especially if you take also the land used for uranium mining into account (those plants consume uranium) which Rod did not.

E.g.
Solar panels on the roof don’t use any land!
When 50% of all roofs are covered with solar panels at latitudes such as USA, they produce twice the amount of electricity (KWh) consumed in USA.
Modern panels from e.g. Sunpower have a capacity of 200W/square meter and the perspective is that the yield will double in the future. Just calculate what that implies if your roof is covered by those panels.

A 10MW wind turbine has a land footprint of less than 10x10meter, that is a power density of 100,000 watts/square meter.

A 10MW wind turbine offshore has no land foot print at all!

Bas Gresnigt's picture
Bas Gresnigt on Dec 10, 2014 3:49 pm GMT

Buy Sunpower X21 panels and get >21.5% efficiency.
Or the new panels announced for next year and get >23% efficiency.

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