Conventional and alternative fuels
19To produce electricity by chemical conversion of energy for industry, housing, the tertiary sector and transport, two choices must be made: the fuel and the combustion process itself, taking into account the balance of carbon (Jancovici, 2007). The optimal system should be:
New technologies to be mobilised for New Caledonia
Conventional and alternative fuels
To produce electricity by chemical conversion of energy for industry, housing, the tertiary sector and transport, two choices must be made: the fuel and the combustion process itself, taking into account the balance of carbon (Jancovici, 2007). The optimal system should be:
flexible to fuels to adapt to market developments, whether conventional such as gaseous fossil hydrocarbons (natural gas, LPG, etc.), liquids (heavy fuel oil, gasoline, diesel, kerosene, etc.), solid (coal), or alternative (hydrogen, biomass, biogas, etc.);
and flexible during its use (modification of the power requested without deterioration of the energy efficiency of the system).
20We will first consider the technical approach.
The potential of conventional fossil fuels for New Caledonia
For a given application, the fuel is selected according to its suitability for the required use, its price, its safety of use, etc., but, for some years now, an additional criterion has been taken into account, its suitability to produce the minimum quantity of CO 2 per kWh dissipated. This quantity is quantified by the emission factor, EF, defined by the mass (in g, kg or ton) of CO 2 emitted per gigaJoule of dissipated fuel or kWh (for example: gCO 2 /kWh dissipated).
Natural gas (NG) is not accessible for New Caledonia
Natural gas (NG) is mainly composed of methane, generally 95%, but its content can vary between 70 and 100%, it can contain other hydrocarbons (propane, butane, ethane, gasoline, etc.), dinitrogen , carbon dioxide, hydrogen sulphide. Natural gas has an average lower calorific value (NCV) of 38.1 MJ/kg or 10.58 kWh/kg (depending on its composition and origin). In 2005, it accounted for 23% of the energy consumed worldwide. Its emission factor (EF) is 201 gCO 2 /kWhth: it is the hydrocarbon emitting the least CO 2 per kWh produced. The world has very large reserves of natural gas, it is very widely used in industrialised countries.
Natural gas is transported from the producing country, or from the fuel depots, to the end user, either by gas pipelines at a pressure of between 90 and 100 bars, or by ships (LNG tankers). In the latter, the NG is transported at atmospheric pressure and at a temperature of -162°C. The temperature is maintained by confining the liquefied gas in thermally insulated tanks; 0.15% of the total volume passes per day in the gaseous state before being consumed by the boat for its propulsion.
Such a ship cannot enter the Caledonian lagoons
The largest LNG tanker in the world, the Provalys (Gaz de France), has a capacity of 154,500 m 3and a draft of 12 m. Such a ship cannot enter the Caledonian lagoons, so the terminal should be located beyond the coral reef. Consequently, for the islands in general, the construction of an LNG terminal is costly, disturbs the ecosystem and is of no interest in comparison with the small quantities of gas likely to be imported. A small LNG tanker carrying 100,000 t of NG will provide electricity for about 9 months in New Caledonia. It is necessary to add the costs linked to the port infrastructure, the investment and the cost of storing the methane in tanks for several months, the losses by evaporation, and the development of a gas distribution network throughout the territory. In addition, its introduction assumes that all players (industrial and domestic) agree on the joint use of gas. Finally, a mono-energy policy is strategically discouraged.
There are floating gas terminal solutions, but the constraints of the coral reef and this cyclonic zone do not seem favourable to this technology. We therefore continue to believe that natural gas is not suitable for use in New Caledonia.
How technology controls the fluctuating cost of these liquid fuels and the competition?
Liquid hydrocarbons have a potentially high and fluctuating cost; liquid hydrocarbons represent 37% of the energy consumed worldwide in 2005 and are used by industry, housing, the service sector and for transport. Their PCI are the highest 39.9 MJ/kg (for heavy fuel oil) or 11.09 kWh/kg. They respectively have an EF of 282 gCO 2 /kWh th (heavy fuel oil) and 267 gCO 2 /kWh (kerosene). For transport, liquid fossil hydrocarbons will remain the most widely used on-board energy for a long time to come, even with the addition of biofuels. For the industry, faced with the high and fluctuating cost of these liquid fuels and the competition of use with transport, they will be less and less economically attractive for long-term use.
Coal is the most accessible
Coal has a very variable composition depending on the deposit. There are two classes, the brown coal with peat and lignite, and the hard coal , the flaming dry, the Gras ( bituminous ) and the anthracite. From brown coal to charcoal , there is an increase in calorific value and a decrease in moisture, volatile matter and ash content. The PCI of coal is between 15 and 27 MJ/kg, i.e. from 4.16 to 7.5 kWh/kg, values depending on the percentages of carbon, sulphur, hydrogen and humidity. Lignite contains little sulphur but contains high humidity. Coal has an EF of 364 gCO 2 /kWh for lignite and 347 gCO 2 /kWh th for anthracite, it is the most unfavourable fuel in terms of GHG emissions, but it represents 24% of the world’s primary energy. The cost and the large reserves indicate that coal is still the most competitive primary fuel currently for producing electricity.