Southern African Natural Gas Advisory Service Service

In terms of natural gas for the production of electricity there are a number of other developments that will continue to increase the demand for gas in this sector, namely:

  Co-firing and re-burn

Gas combustion technologies, such as co-firing and re-burn in conventional coal fired power stations can reduce harmful emissions while preserving electric utilities investment in coal generation. Natural gas can be burned with coal to reduce emissions of sulphur dioxide and nitrogen oxides that both cause acid rain.  

   Co generation

With an increasing number of industrial plants and commercial energy installations using natural gas, cogeneration is a growing source of electricity production. Co generation involves the simultaneous production of steam for heating applications and electricity. Major industrial sites that use large amounts of heat for various types of processing frequently have surplus thermal energy that can be used to generate electricity for their own use and for sale to the national electricity grid.

In the last thirty years the concept of co generation has become more widespread as the necessary equipment and plant has become smaller and more versatile.

- The flexibility and controllability of natural gas fired power plant. Traditionally natural gas was mainly used for ‘peaking plant’ to provide instant power during high levels of demand at certain times of the day, week or due to seasonal variations. With the many other benefits of natural gas that have arisen in more recent years, it is increasingly also a preferred primary energy for base load electricity generation. To be able to obtain the necessary operating economies with coal power stations they usually have to be very large to obtain economies of scale. With natural gas these limitations do not exist and generation plants come in a wide range of sizes and modules. Large coal fired power plants also take time to ‘fire up’ and to bring onto the grid whereas with natural gas plant it is almost instant, depending on the type of generation technology being deployed.           

- The proven comparative environmental benefits of using natural gas for power generation rather than other fossil fuels. Natural gas emits fewer  greenhouse gases, wastes less primary energy, there is no ash or other residues and it is supplied without any degradation of the local landscape.

- It is easier to obtain planning and other necessary approvals to construct a natural gas fired power plant than either a coal or nuclear plant. This is because they are smaller, safer, have little local environmental impact and can be operated almost unobtrusively to local residents. They have a small ‘footprint’ in comparison with either coal or nuclear power stations. No fuel storage, handling or disposal facilities are required and the natural gas is delivered invisibly underground via a gas pipeline.

- Gas is safe. In comparison with coal, oil and especially nuclear based electricity generation plant, natural gas has an outstanding safety record. Unlike coal and certainly nuclear plant, gas plants can be shut down quickly should the need arise.

- Flight from nuclear power in many countries across the world following the continuing potentially  disastrous long term consequences  of the ‘melt-downs’ with Japanese nuclear plant will call for more natural gas plant to be constructed. This trend is already taking place in Asia, Europe and the U.S.A.

    Fuel cells

Major research and development has been focused in recent years on the manufacture of small competitively priced natural gas fuel cells that produce electricity from a chemical reaction.  These are now available for use in the home at a cost that is around the same as a comparable solar photovoltaic system. As this technology is further commercialised the time is rapidly approaching when even households will only need a natural gas supply to meet all their energy needs.

Co generation

Electricity Generation

Natural gas has become the fuel of choice for electricity generation because of its ‘green properties’ when compared to coal or oil and because it is cheaper and faster to build gas fired generation plant; and it is safer than nuclear as a  source of heat and steam to turn the turbines to produce electricity. Just as one illustration of this growth in the use of natural gas for electricity generation, in the European Union of 27 countries in 1990 some 7.5% of electricity was produced using natural gas. Today some 20% of all the electricity produced in the 27 EU countries is generated using natural gas and this trend continues. Similar trends exist in the U.S. and many other countries around the world.

Although coal continues to be used to generate huge volumes of electricity and this is likely to continue for years to come due to the large indigenous reserves of coal that many countries have together with massive  historical investments in coal fired plant, the world’s reliance on coal for electricity generation is set to diminish in the future. Three key developments have taken place in recent years whereby natural gas is set to continue to challenge coal’s dominance in the electricity generation sector. They are as follows:

1. A number of ‘game changing’ technological developments such as the very rapid application of cost effective natural gas liquefaction technology and the acceleration of the LNG global shipping and supply trade.  Natural gas can now be made available anywhere in the world on highly competitive terms for large power plants than competing fossil fuels.  The other technological game changer has been the ever increasing efficiencies with natural gas power station technology in comparison with coal fired plant.

2. The vast increase in the global reserves of natural gas that have been proven in the last few years. Natural gas is now a widely available clean fossil fuel that can be supplied from a diverse range of countries and suppliers. This means that the security of supply of natural gas is largely assured.

       3. The global climate change lobby and more restrictive regulations regarding the use of ‘dirty’ coal for power generation and increasing pressure on                utilities to drastically reduce their carbon footprint. These pressures are also set to mount in South Africa with the new carbon tax in 2015.   

In addition to the gradual demise of coal fired power generation and the substitution of natural gas there are several other reasons for this flight to natural gas for electricity generation and these are described below:

-  Advanced gas turbine technology which may be used for new power plant investments or the refurbishment of existing power stations now     offer  efficiencies of up to 56% with combined-cycle technologies compared with 33% efficiency in conventional power stations. Such     efficiencies  create huge competitive advantage for electricity producers ensuring that operating costs are lowered and maximum output of     electricity is  obtained from the primary energy used, namely natural gas. Such efficiencies are extremely difficult to replicate with any of the     alternative  fossil fuels.  With natural gas these benefits can be passed onto consumers with lower and more stable electricity prices.  

-  Compared with coal fired power stations, natural gas combined cycle generation plant affords lower capital costs, a much shorter construction     time, minimal environmental impact and the flexibility to add modules as more generating capacity is required.  This reduces the debt burden

    that utilities have to absorb and manage with large new coal fired power station investments that cost many billions.        

-  The relentless and necessary drive for improved energy efficiency. In other words obtaining the same from less which in the case of natural gas      electricity generation can provide 23% more electricity from the same equivalent energy input, than coal, when using modern generation gas      fired power plant.

-  De-regulated and highly competitive electricity markets. As deregulation has swept across many countries and their  energy markets, the need      to produce electricity in the most cost effective manner becomes paramount. Increased  competition is putting relentless pressure on   

    electricity producers to move to more  efficient and lower cost generation technology and primary fuels.

Distributed generation

With various technical developments and many electricity utilities wishing to buy power from independent power producers, combined heat and power (CHP) facilities are now familiar in many locations where natural gas is available.  Such facilities enable the production of hot water and heat for space heating and cooling while also generating electricity.  CHP plant is extremely efficient and energy cost saving since they provide electricity, hot water and steam from the single source of clean low cost natural gas.  Such installations have become popular in hotels, hospitals, universities, retirement homes, computer centres and other commercial premises that are able to avoid the cost of using grid electricity and when their own demand is low, selling their surplus power to the electricity utility. With the rising cost of grid electricity together with the increasing unreliability of power from some national networks, smaller scale distributed power generation from natural gas and other energy sources such as renewable, waste and biomass are set to increase in the future.

Standby generation

As some national electricity supply networks have become less reliable, not able to guarantee consistent and reliable electricity supplies, more and more premises have installed standby generation facilities. Shopping centres, hospitals and computer installations and other sensitive operations have commonly had some form of electricity back-up system in cases of emergencies. With the advent of low cost and controllable natural gas, many of these facilities are being enlarged to obtain the inherent benefits of natural gas to reduce site energy costs and unreliable energy supply.  

Displacement of electricity at point of energy use.

There is another aspect of increasing natural gas use that impacts electricity generation and supply. Electricity is an expensive and wasteful energy source for most thermal applications involving the generation of heat, hot water, food cooking and cooling at point of use.

Natural gas is increasingly being used to displace electricity for such applications at point of use. Air conditioning in the USA is a good example with  new generation natural gas heating and ventilation technology now displacing conventional electrically driven systems in offices and public buildings.