Peak Oil - A crisis facing the entire planet

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.

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?

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.

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.

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

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.

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.

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:

There is no cost in buying the land and preparing the site. Roofs are owned by those who own the rest of the building.
No environmental impact .
The transmission losses are much lower because the load is on the same site as the supply.
The value of the PV electricity is also higher because it is equal to the selling price of the grid electricity which has been replaced, rather that to the cost of generating it.
Householders, businesses and local authorities can sell their surplus to the grid.

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.