Gunnar Berge: Electrification of the Shelf

02/05/2007 As a solution for reducing Norway's CO2 emissions, removing power plants from the shelf and replacing them with energy from land is neither simple nor cheap, writes director general Gunnar Berge.

In recent years we have seen presentations which make it seem almost easy to remove power plants from the offshore oil and gas facilities and compensate with transmission of energy from land. This is not the case.

Although the offshore power plants currently account for about 25 per cent of Norway's total emissions of carbon dioxide (CO2), the costs of electrifying the shelf, in other words, operating the facilities using power from land, will be substantial. The benefit to the environment is also unclear.

 The Norwegian Petroleum Directorate (NPD) and the Norwegian Water Resources and Energy Administration (NVE) have carried out a study to evaluate the possibility of replacing turbines and generators that produce electricity offshore with power from land.

Power from land will reduce the emissions of CO2 and nitrogen oxides (NOx) on the shelf, but it will be very expensive. The emissions of CO2 and NOx are closely connected. Gas combustion in turbines, flaring of gas and diesel consumption on the facilities are key emission sources for both CO2 and NOx. NOx are not greenhouse gases as such, but they do have several different effects on the environment, such as acidification of watercourses and soil.

Calculations made by the NPD and NVE show that the costs of measures to electrify the shelf will be high compared with today's CO2 tax, NOx tax and the expected international CO2 quota price.

When the Low Emission Committee submitted its report last year, it relied on the NPD's conclusions that the costs of modifying the offshore facilities to prepare them to receive power from land would be too high. Therefore, the Low Emission Committee recommended that existing facilities not be modified.

Instead, the Committee suggested reducing the emissions of greenhouse gases from production and transportation of petroleum by ensuring that future process facilities were built on land to the extent possible, and that they be run using CO2-neutral electricity. Alternatively, the Committee proposed supplying electricity from land via cables where this was possible from a cost perspective, or possibly in combination with wind turbines along the coast. The Committee recommended further work on process improvements on the facilities.

However, the offshore power plants are not inefficient. They are relatively new and well-maintained, and they are therefore reasonably energy-efficient. Energy facilities on land are generally more energy-efficient than offshore energy plants, but CO2 cleaning (also referred to as scrubbing) in land facilities requires energy, as does transportation. This means that there is little or no efficiency gain in electrification using energy from land from which CO2 has been cleaned.

The efficiency of a gas power plant on land depends on where the power plant is located. A gas power plant will normally be built near the landing site for the gas, which may be far from densely populated areas. This means that the residual heat from the plant has limited value, as there are few potential users.

Energy plants with a total output of about 4250 megawatts (MW) are installed on the Norwegian shelf. This is equivalent to 8-10 gas power plants the size of Kårstø. About 21 terawatt-hours of electric power are produced on the shelf. In comparison, production of electric power on the Norwegian mainland in 2006 was about 121 terawatt-hours. The energy produced offshore is significant. However, we also know that energy consumption on land in Norway in a normal year is greater than the energy produced, which means that there is no surplus of domestic power to supply the shelf. Therefore, this power must be obtained in some other way, either by increased import - which will largely mean coal power or gas power without CO2 cleaning - or through new domestic power development. New developments of hydroelectric power are not considered to be a realistic alternative.

At the end of 2006, there were 52 producing fields on the Norwegian shelf, while only 30 of the fields had regular production of power. The other fields do not have their own process facilities, but are linked to other facilities.

The need for power and energy efficiency on these fields varies over time and according to a number of field-specific factors. The most important factors governing the need for power are pressure development, transportation needs and production development of oil, gas and water over time.

Significant investments are required to electrify the shelf; for sea cables, conversion stations, new platforms and costs associated with modification of existing facilities, regardless of whether the power comes from hydroelectric power plants, gas power plants, gas power plants with CO2 treatment or imported power.

If the shelf is electrified without production of pollution-free electricity in Norway, it is uncertain whether the result will be a net reduction of CO2 overall. This is due to the loss of energy associated with transmission to the shelf and the fact that production increases in Europe for several years will come from existing coal power plants with significant CO2 emissions. However, electrification of the shelf will lead to substantial reductions in NOx.

 

Updated: 04/09/2009