Natural gas: general

I don't want to go into the political aspects of whether Cyprus should have either an onshore or an offshore regasification scheme but I will touch on the technical aspects. My view is that Cyprus should not use natural gas at all for electricity generation and I'll explain why.

It is claimed that natural gas is the least polluting fossil fuel. If you count only the gas, as it is delivered to the burner or the turbine, this is true. Nevertheless, for every kilogram of gas burnt in a boiler or a turbine, 2.74 kg of carbon dioxide are emitted into the atmosphere - yes, very nearly 2¾ kg. This translates to 0.20 kg of CO₂/kWh generated in an average power station. This compares with about 0.28 kg for the currently used fuel oil, depending on the quality, and 0.34 kg for coal. Unfortunately, this comparison is unfair, because the natural gas itself is a bad greenhouse gas, 20-50 times worse than CO₂. The crunch is that the extraction, purification, liquefaction, transport and regasification all create emissions of methane, so that, if you count the CO₂ equivalence from the wellhead to the power station, the emissions may be worse than even coal-burning and certainly worse than oil. For a full technical explanation, with typical figures, please consult this website.

Production of natural gas

To have natural gas available at a Cyprus power station, there is a series of operations. When reading this, please remember that each time there is an escape of gas, the greenhouse gas in the atmosphere balance sheet becomes more positive (i.e., climate change becomes more pronounced). We can take, as an example, Qatar as our starting point, as this is one of the nearest production units. The first thing is that a well is drilled. As the borer reaches a "pocket" of gas under considerable pressure, large quantities will escape until the well can be cased and "Christmas treed". The "Christmas tree" is a complex pipework system designed to crudely separate the gas from water, oil and solid matter such as sand. It is regularly purged until only gas escapes. After this, as a general rule, many such wells are drilled within a radius of a few 100 m and a web of low diameter pipes connect the Christmas trees to a purification plant. These pipes are jointed and leaks do occur, along with small leaks from around the casing.

After purification, which also causes emissions in normal exploitation, the natural gas is typically 99% pure methane. It is then compressed and sent via a pipeline to a liquefaction plant where it is converted into liquid natural gas (LNG) at -163°C and close to atmospheric pressure. The compression, transport and liquefaction all entail considerable energy consumption (more CO₂ emissions) and fugitive emissions of gas. The LNG is then stored at low pressure in special double-walled, nickel-steel tanks with vents to prevent a build-up of pressure. The LNG is pumped into tankers with similar tanks. The action of connecting and disconnecting the tanks also involves escapes of gas.

Up to recently, the boil-off from the tanks was used to propel the tanker to its destination. This is no longer possible because the improved tank insulation means less boil-off and the modern ships burn fuel oil (emitting more  CO₂!). The boil-off is possibly used to drive the ship's generators. However, the question arises as to what happens when the tanker's fuel consumption is reduced, such as in port or waiting in the roads. As the tanks are low pressure types, the only solution is to vent the gas to atmosphere.

At the ship's destination, the LNG is discharged into tanks, similar to those used for the storage after liquefaction. From there, it is pumped into a regasification plant which heats it until the required amount of gas is produced to meet the demand. The regasification plant also treats boil-off gas from the storage tanks and, in some cases, from the tanker. It sounds simple, but the plant is, in reality, quite complex to ensure that supply equals demand.

All stages involve fugitive leaks and energy consumption as explained op. cit., so that the 2.74 kg CO₂ per kg of gas easily can reach 4 kg CO_2equivalent  or more, by the time it is burnt.

Advantage of LNG

There is one significant advantage of using LNG. If it is used in a small gas turbine, it can be rapidly brought on line in the event of a sudden, unforeseen, increase in demand, such as may be occasioned by an abrupt and unexpected change in the weather or an historic event causing everyone to rush to switch on their television. Conventional thermal plants have a longer lag time in adjusting to changes.

If variable renewable energy becomes significant, then this rapid response time becomes doubly advantageous if it suddenly clouds over or the wind stops blowing.

Problems specific to Cyprus

Cyprus will be a small consumer of LNG, compared to the major ones. The time taken for a tanker to discharge its cargo from the moment of stopping in the roads to the time that it moves off again is little different if it unloads 15,000 or 250,000 m³ of LNG, typically one day. It is clear that it is not profitable for a large tanker, costing $300 million, to stop to partially unload one-tenth or less of its cargo. This implies that only small LNG-tankers can supply Cyprus. However, there is a problem here; small tankers are not welcome at the loading quays because it is similarly more profitable for the supertankers to load. This means that the small tankers may have to wait in the roads for many days or weeks before there is a gap between the larger vessels. This obviously means higher costs, reflected in the price paid for the LNG, but it also means that a larger strategic buffer stock is required on the island, as it is impossible to allow a tank to be completely emptied, because any air drawn into a tank, will form a potentially explosive mixture.

Another problem is the site for the regasification plant. Proposals have been made to have either a fixed or a floating unit. The latter is more expensive but theoretically can be completed sooner. I say 'theoretically' because no one knows the lead time as it is untried technology or even whether it can be done with the necessary safety features. However, it occurs to me a floating unit in a known earthquake region seems very hazardous, if seismic activity broke it free from its moorings. Also, it would complicate the unloading process from the tanker, because the relative movement from swell would be greater than with a land-based plant. All-in-all, speaking as an engineer, I feel that a conventional land-based plant would seem the best option.

Conclusion

I don't believe that LNG is a good option for power generation in Cyprus. It is true that it will appear to reduce greenhouse gas emissions by about 28 percent, within the island, to generate a given quantity of electricity, compared to using fuel oil. The truth is that will increase them but this will happen mostly outside Cyprus. This is an ostrich-like attitude pretending it doesn't happen because it is not in our own backyard.

So what is a good option for this country? To start with, a fixed thermal power station burning household rubbish would add 10 percent to our capacity. This is a tried, tested and successful technology, used in many places round the world. It offers the additional advantage that it reduces landfill requirements by 80-90 percent, the ashes also being sterile. The downside is that the plant is about 30 percent more expensive in capital costs than a conventional thermal station, although this is rapidly amortised by the fact that the fuel is free. The second echelon is, of course, variable renewables, such as wind and solar. The third echelon seems to me to be the inevitable one, which will not be popular: nuclear fission. If a latest generation EuroPR power station is envisaged rapidly, it could be in service just in time for when the energy demands of the island will require that 1.6 GW extra capacity, about 2014, but it will require action now to prevent a penury of electricity. This will keep prices down, as well.

Whatever options are taken, there is another factor to consider: we shall require more water. Without going into the causes of this, further desalination plants will become increasingly necessary. These are very energy-intensive and if the energy comes from fossil fuels, we shall never keep up with our Kyoto Protocol and EU commitments. As I see it, nuclear power is the only way we can keep up with our ever-increasing demand for good water.

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