Energy Alternatives

Let us have a look at some of the alternative energy sources that have been mooted, dabbled with, researched, piloted or are actually already in use.

• Wind
• Solar
• Wave
• Tidal
• Nuclear
• Bio-fuels
• Hydrogen

Can any of these either by themselves or in combination take over from oil?

Can any of these lead us to a bright new future or are they just overrated, irrelevant and even dangerous suggestions?

 

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Solar

The sun always rises. It is dependable, infinite and doesn’t cost us a penny. It doesn’t generate pollution which is hazardous to the environment or to human health; no carbon dioxide is generated.

Even in rainy and cloudy Britain the sun rises every day. In fact on a bright, sunny day, the sun shines approximately 1,000 kilowatts of energy per square metre of the land surface, (insolation) and if we could collect all of that energy we could easily power our homes and offices for free so why are we not using all that free energy?

 
Photo: State of the art trackable solar panel array in California

Basic physics

Let’s have a look at the basics. Most readers will be familiar with solar cells seen on calculators, garden lamps. Some city centre parking meters are powered by solar as are data collection stations, air sampling stations besides motorways. They are powered by photovoltaic cells. Photovoltaics, as the word implies (photo = light, voltaic = electricity), convert sunlight directly into electricity. The PV cells are made of special materials called semiconductors such as silicon, which is currently the most commonly used.

Basically, when light strikes the cell, a certain portion of its energy is absorbed within the semiconductor material. This means that the energy of the absorbed light is transferred to the semiconductor. The energy knocks electrons loose, allowing them to flow freely. PV cells also all have one or more electric fields that act to force electrons freed by light absorption to flow in a certain direction. This flow of electrons is an electric current, and by placing metal contacts on the top and bottom of the PV cell, the current can be drawn off to use externally. This current, together with the cell’s voltage (which is a result of its built-in electric field or fields), defines the power (or wattage) that the solar cell can produce.

Power = current x voltage

A typical PV cell will only absorb only about 15% of the sunlight’s energy? Visible light is only part of the electromagnetic spectrum. Electromagnetic radiation is not monochromatic - it is made up of a range of different wavelengths, and therefore energy levels.

Since the light that hits a PV cell has photons with a wide range of energies, it turns out that some of them won’t have enough energy to form an electron-hole pair. They’ll simply pass through the cell as if it were transparent. Other photons have too much energy. Only a certain amount of energy, measured in electron volts (eV) and defined by our cell material (about 1.1 eV for crystalline silicon), is required to knock an electron loose. This is the band gap energy of a material. If a photon has more energy than the required amount, then the extra energy is lost (unless a photon has twice the required energy, and can create more than one electron-hole pair, but this effect is not significant). These two effects alone account for the loss of around 70 percent of the radiation energy incident on a typical PV cell.

Losses

It might be thought that we find or devise and use a material with a really low band gap, so we can use more of the photons. Unfortunately, the band gap also determines the strength (voltage) of the electric field, and if it’s too low, then what is gained in extra current (by absorbing more photons), is lost by having a small voltage. The optimal band gap, balancing these two effects, is around 1.4 eV for a cell made from a single material.

Other losses occur as well. Electrons have to flow from one side of the cell to the other through an external circuit. The bottom of the cell could be covered with a metal, allowing for good conduction, but if the top is completely covered, then photons can’t get through the opaque conductor and all of the current is lost (in some cells, transparent conductors are used on the top surface, but not in all). If the contacts are only placed at the sides of the cell, then the electrons have to travel an extremely long distance (for an electron) to reach the contacts. Silicon is a semiconductor - it’s not nearly as good as a metal for transporting current. Its internal resistance (called series resistance ) is fairly high, and high resistance means high losses. To minimize these losses, the cell is covered by a metallic contact grid that shortens the distance that electrons have to travel while covering only a small part of the cell surface. Even so, some photons are blocked by the grid, which can’t be too small or else its own resistance will be too high.

A stationery set of cells on a static roof does not make the most of the insolation. Ideally a moveable platform on which to mount the panels to track the passage of the sun would be employed. The panels should be inclined at an angle equal to the area’s latitude to absorb the maximum amount of energy year-round. A different orientation and/or inclination could be used if one wants to maximize energy production for the morning or afternoon, and/or the summer or winter. Of course, the modules should never be shaded by nearby trees or buildings, no matter the time of day or the time of year. In a PV module, even if just one of its 36 cells is shaded, power production will be reduced by more than half.

Although the British average insolation is 1000Kw/m2 there are huge variations both in terms of geography, aspect and seasonality

Table: Annual average UK insolation

Insolation (yearly average in KWh/m2)
Edinburgh	825
London	953
Plymouth	1172

 

Seasonal variation (daily average average in KWh/m2)
Plymouth - June	5.70
Plymouth - December	0.95

Source: NASA

Other factors are rainfall and cloudy days, as well as altitude, humidity , and other more subtle factors.

The electricity generated by PV modules, and extracted from batteries if used, is direct current, while the electricity supplied by the power utilities (and the kind that every appliance in every house and office uses) is alternating current. So an inverter is needed which converts DC to AC. Some PV modules, called AC modules, actually have an inverter already built into each module, eliminating the need for a large, central inverter, and simplifying wiring issues.

Once installed, a PV system requires very little maintenance (especially if no batteries are used), and will provide electricity cleanly and quietly for 20 years with new generation PC cells now expected to last as long as 30 years. It is possible to sell surplus electricity to the power utilities by hooking up the electricity generator to the national grid via a meter which measures the amount of electricity transferred to the grid.

Diagram to illustrate roof based PV system

Energy Payback

There are some misleading or just plain ignorant claims that PV cells demand more energy in their manficature than they produce in their lifetime, making them a flawed energy alternative. These claims are untrue.

Erik Alsema, a Dutch engineer at Utrecht University has calculated that the manufacture of first generation single crystal PV cell would need an input of 600 KWh to produce one square metre of surface area, and to manufacture new generation multi-crystal cell would require 450 KWh for the same 1m2.

Assuming 12% conversion efficiency (standard conditions) and 1700 kWh/m 2 per year of available sunlight energy (the U.S. average is 1800), Alsema calculated a payback of about 4 years for current multicrystalline-silicon PV systems. Projecting 10 years into the future, he assumes a “solar grade” silicon feedstock and 14% efficiency, dropping energy payback to about 2 years.

Other recent calculations generally support Alsema’s figures. Based on a solar-grade feedstock, Japanese researchers Kazuhiko Kato et al . calculated a multicrystalline payback of about 2 years (adjusted for the U.S solar resource).

Adjusted for UK insolation, the payback period is extended from 4 years to 6.5 years. That means the energy generated by a PV cell during the first 6.5 years of its working life is needed to compensate for the energy involved in its manufacture with the remaining 23.5 years working life to generate net energy.

Domestic and industrial needs

Solar currently powers calculators and garden lamps but can it be used for electricty generation on a larger scale.

A typical UK household consumes about 4000 KWh of electricity a year. We have seen that the insolation in the UK is 1000KWh/m2 and we have seen that the conversion of solar light to electricity is average of 15%. Simple arithmetic shows that to provide all the 4000KWh a PV module covering 26.7 m2 is needed. At current prices it works out at about £18,000. Prices are falling as demand increases but the financial cost is prohibitive to most households.

Industrial scale production of electricity is unlikely. Just as we discussed with wind generation of electricty and stated that wind wa a low denisty power source the same is true of solar.

Here is an example. A typical electric train can consume anything from 36 to 60 KWh/mile. Remember the insolation figure of 150KWh/yr/m2 of PV cells or 0.41 KWh/day/m2 well it would take 87m2 of PV cells to propel a train for one mile. Put another way just to power the 19 daily trains operated by GNER on the 415 mile Edinburgh to London route would require 685995m2 which is the equivalent of 170 football pitches! Double the area if you want to power the trains on the return Edinburgh bound journey! Of course the panels are not laid out on the ground, but are set angled at an elevation to gain maximum insolation but the area gives a reasonable illustration of what we can expect to do if we want to run electric trains on solar power!

Now think of all those hundreds of trains, electric trams and buses running across the lenght and breadth of the UK and one realises that replacing oil with solar is not a starter. We haven’t even mentioned the 26 million vehicles on Britain’s roads which some might dream can be relaced by electric cars! Huge swathes of flat treeless countryside would need to be covered in PC cells (using hilly or mountainous land would reduce generating capacity, likewise the shadows cast by trees would render such forested areas useless).

The impact on the British countryside would be enormous with disastrous effects on flora, fauna, not to mention the impact on accessibility to the countryside and sacrificing perfectly good agricultural land.

Solar power is not going to help our transportation requirements in any significant way. In fact as we shall see none of the suggested alternatives can replace the usage of oil for our transportation demands.

For the foreseeable future solar will be big business for use on Britain’s rooftops where:

Conclusion

Although costly in monetary terms we do have a real candidate here for dispersed applications which use the currently unused or underused space on the roofs of British homes offices and other buildings.

One of the pledges of a BNP local council will be to install solar cells on the roof of every local council building including its housing stock. We will provide generous grants to private householders as well and simplify the bureaucracy and planning issues. The cost will be recovered by the sale of surplus electricty to the national grid.

Unless we really want to sacrifice huge areas of the countryside and perfectly good productive agricultural areas in lowland Britain the scalability of the generation of electricity is just not possible. Flat deserts with cities not too distant are the best locations for industrial scale solar conversion. California, parts of Australia, south America and north Africa could benefit from the technology but solar use in the UK is likely to stay on the rooftops.

 

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Hydrogen

We could involved in some in depth chemistry here. But this is a political site and not a chemistry site so we need to keep things basic for the lay persons.

Essentials

The basics of hydrogen technology are as follows.

1. Hydrogen is the most abundant element in the universe. It is found on earth in many forms but the most practical one for human use is the globally abundant water, good old H2O.

2. Sending an electric current through water splits water molecules into hydrogen and oxygen. Every schoolchild will have performed this experiment. It is called electrolysis and for every molecule of water, two atoms of hydrogen and one atom of oxygen are produced. Energy in leads to hydrogen and oxygen out.

3. The reverse process of combining atoms of hydrogen with oxygen generates energy which can be captured as electricity, the only other product is a harmless one - water!

4. The reverse process is the basis of a fuel cell, where hydrogen and oxygen react with one another on a surface of something called a catalyst, a chemical which facilitates the chemical reaction.

5. Fuel cells have been built in laboratories and pilot units. The most common catalyst used in these pilot and experimental units is platinum.

6. The hydrogen can be produced by a variety of means but the most attractive option for a future hydrogen based economy would be electrolysis. The electricity for electrolysis would have to be generated from a renewable source in a post oil situation and the hydrogen stored and distributed via pipelines or tankers.

7. It is envisaged that fuel cells will be used to drive motor vehicles. Motor vehicles will be filled at “gas stations” in a similar way to existing petrol stations. The gas stations might be the same places where the hydrogen is produced. Arrays of solar panels on the roof of a gas station will generate the electricity to perform the electrolysis. The hydrogen will be stored on site and vehicle drivers will come along and refuel their fuel cell driven cars.

Clean, pollution free, sound very neat doesn’t it, except for a few major shortcomings.

Lightest element

First off, because hydrogen is the simplest element, it will leak from any container, no mater how strong and no matter how well insulated. For this reason, hydrogen in storage tanks will always evaporate.

Hydrogen is very reactive. When hydrogen gas comes into contact with metal surfaces it decomposes into hydrogen atoms, which are so very small that they can penetrate metal. This causes structural changes that make the metal brittle.

Perhaps the largest problem for hydrogen fuel cell transportation is the size of the fuel tanks. In gaseous form, a volume of 62,880 gallons of hydrogen gas is necessary to replace the energy capacity of 20 gallons of petrol. The arithmetic doesn’t look good so far.

However demonstrations of hydrogen-powered cars have depended upon compressed hydrogen. Because of its low density, compressed hydrogen will not give a car as useful a range as gasoline. In addition compressed hydrogen fuel tank would be at risk of developing pressure leaks either through accidents or through normal wear, and such leaks could result in explosions.

If the hydrogen is liquefied, this will give it a density of 0.07 grams per cubic centimetre. At this density, it will require four times the volume of gasoline for a given amount of energy. Thus, a 15-gallon gas tank would equate to a 60-gallon tank of liquefied hydrogen. Beyond this, there are the difficulties of storing liquid hydrogen. Liquid hydrogen needs to be stored at -253 C. That is colder than the surface of planet Pluto!

Refrigeration costs

Beyond this, there are the energy costs of liquefying the hydrogen and refrigerating it so that it remains in a liquid state. No studies have been done on the energy costs here, but they are sure to further decrease the Energy Return on Energy Invested (EROEI) of hydrogen fuel.

A third option is the use of powdered metals to store the hydrogen in the form of metal hydrides. In this case, the storage volume would be little more than the volume of the metals themselves. Moreover, stored in this form, hydrogen would be far less reactive. However, as you can imagine, the weight of the metals will make the storage tank very heavy.

The basic problem of hydrogen fuel cells is that the second law of thermodynamics dictates that we will always have to expend more energy deriving the hydrogen than we will receive from the usage of that hydrogen. The common misconception is that hydrogen fuel cells are an alternative energy source when they are not. They are a form of energy storage - a big difference!

Because of the second law of thermodynamics, hydrogen fuel cells will always have a bad EROEI. If fossil fuels are used to generate the hydrogen, either through the Methane-Steam method or through Electrolysis of Water, there will be no advantage over using the fossil fuels directly. The use of hydrogen as an intermediate form of energy storage is justified only when there is some reason for not using the primary source directly. For this reason, a hydrogen-based economy must depend on large-scale development of nuclear power or solar electricity.

Therefore, the development of a hydrogen economy will require major investments in fuel cell technology research and nuclear or solar power plant construction. On top of this, there is the cost of converting all of our existing technology and machinery to hydrogen fuel cells. And all of this will have to be accomplished under the economic and energy conditions of post-peak fossil fuel production.

Further reading

For those readers who want to find out more about the underlying chemistry and physics of fuel cells and hydrogen should have a look at the following:

http://www.eere.energy.gov/hydrogenandfuelcells/education/abcs.html

 

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Wind Power

The most talked about alternative and one which is being rolled out across the British countryside.

Proponents of wind turbines claim that wind represents a free, unlimited source of energy. It does have its attractions.

Advantages

It’s clean. Wind power does not produce dangerous waste, nor does it contribute to global warming because it generates no carbon dioxide.

It’s abundant and reliable. The UK is the windiest country in Europe and the resource is much greater during the colder months of the year, when energy demand is at its highest. Technology is being developed to store wind power as hydrogen which can then be used to power fuel cells in power stations and in vehicles.

It’s affordable. The first offshore wind turbines in the UK are producing power more cheaply than our newest nuclear power station.

It works. Denmark already gets 20% of its electricity from wind power. A turbine can turn when wind speeds are just 9mph.

It creates jobs. The wind industry could bring thousands of new jobs to the UK, many of them using offshore engineering skills used by the declining oil and gas industry. If offshore wind were developed to supply just 10% of the UK’s electricity, then 36,000 jobs could be created.

It’s safe. Unlike nuclear power stations, wind turbines are unlikely terrorist targets. The rotors are automatically shut down when wind speeds reach in excess of about 60mph.

Opposition to wind turbines on Britain’s hills and coastlines on the basis of “spoiling the view” is subjective. What some might see as brutish industrialisation of the hilltops, others see elegant, graceful and powerful monuments to Man’s ingenuity and harnessing of nature’s bountiful gifts. A study by the RSPB also debunked the myth that wind turbines kill large numbers of birds. The available evidence suggests that appropriately positioned wind farms do not pose a significant hazard for birds. However, evidence from the US and Spain confirms that poorly sited wind farms can cause severe problems for birds, through disturbance, habitat loss/damage or collision with turbines.

Wind and likewise solar energy suffer from four fundamental physical issues which prevent them from ever being able to replace more than a tiny fraction of the energy we get from oil. These issues are:

a. lack of energy density,
b. inappropriateness as transportation fuels,
c. energy intermittency,
d. inability to scale.

Energy Density

Density refers to the amount of energy per unit of volume of an energy source. Oil is a very, very dense energy source. Coal is quite dense per unit of energy, but much more bulky than oil. Unfortunately, solar power has very low relative energy density. Density, is often, but not always, associated with the energy profit ratio, the ratio between how much energy you get for how much you expend to get it. Generally, speaking, the higher the density, the higher the energy profit ratio. Oil energy profit ratios were well over a 100 to 1 in the early days of the oil age, that is 100 units of energy gained for every unit expended to get it. Oil has slipped to about 20 to 1 for most old discoveries now and to around 8 to 1 for new discoveries which are getting harder and harder to extract and are of lower quality (i.e., lower energy density). Compare this to 4 for nuclear power, 2.5 for biodiesel, 2 or more for wind, and slightly more than 1 for solar. Oil and coal (about 10 to 1) continue to be favoured because of this ratio.

To put this into perspective, the Rye House power station at Hoddesdon, Hertfordshire, generates 715 MW of electricity from natural gas coming in from the North Sea. Built in the early 1990s it is a very efficient producer of electricity. Output from the station is enough to meet the daily power needs of nearly a million people - almost the population of Hertfordshire. To produce the same amount can you guess how many wind turbines might be needed. 50? 100? 1000? Based on a typical turbine output of 0.70MW the actual answer is 1020! According to Scottish Power the Black Law turbine farm in South Lanarkshire will be the biggest onshore project in the UK. It will contain 62 individual turbines and cover an area of 24.5 square kilometres. Our theoretical 1020 turbine farm would need an area of 403 square kilometres or roughly an area 11 miles by 11 miles - 25% of the land area of the entire county of Hertfordshire!

Transportation

Over ninety percent of our transportation fuel comes from petroleum fuels (gasoline, diesel, jet-fuel).

Unfortunately, solar and wind cannot be used as industrial-scale transportation fuels unless they are used to crack hydrogen from water via electrolysis. The electrolysis process is a simple one, but unfortunately it consumes 1.3 units of energy for every 1 unit of energy it produces . In other words, it results in a net loss of energy. You can’t replace oil - which has a positive EROEI of about 30/1 - with an energy source that actually carries a negative EROEI.

Assuming away this not-so-minor problem, where are we going to get the energy, capital, and time necessary to replace a significant portion of the following:

1. 700 million oil-powered cars traversing the world’s roads;

2. Millions of oil-powered airplanes crisscrossing the world’s
skies;

3. Millions of oil-powered boats circumnavigating the world’s
oceans?

On top of that, we need to completely overhaul/retrofit the multi-trillion dollar infrastructure responsible for the fuelling and maintenance of numbers one through three.

Intermittency

Unlike oil and gas, which can be used at anytime of the day or night, solar and wind are dependent on weather conditions. This may not be that big of a deal if you simply want to power your household appliances or a small scale, decentralized economy, but if you want to run an industrial economy that relies on airports, airplanes, millions of miles of highways, huge skyscrapers, 24/7 availability of fuel, etc., an intermittent source of energy will not suffice.

The energy produced from solar, wind, and other green alternatives can be stored in batteries, but battery technology is woefully inadequate for the scale of our problem.

Scalability

The problems of using a low density energy source such as wind was demonstrated above. Not even the most enthusiastic wind turbine proponent claims that all of the UK’s electricity requirements will be satisfied by wind, but by way of illustration, we showed above that the electricity requirements of 1million households and businesses in Hertfordshire could be met by turbines covering a 11 by 11 mile plot. What of the UK’s 60 million residents? What size farm would we need? A 24,180 square kilometre plot equivalent to the combined size of Cumbria, Northumbria, Co Durham and North Yorkshire!

Conclusion

Great for powering the electricity requirements of caravans, isolated homes and small communities but its low energy density makes it impossible to provide anything other than a tiny fraction of the UK’s generating capacity.

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