1.1 BACKGROUND

If the industries and accustomed lifestyles of the economically well — developed nations are to be preserved, their aging high-capacity (0100 MW) electric power plants will soon require replacement with reliable units having lower carbon emissions and environmental impacts. Legally binding national targets [1] on carbon emissions were set out by the European Union in 2008 to mitigate their now unequivocal effect on global climate change. In 2009, the UK’s Department of Energy and Climate Change [1] announced ambitious plans for a 34% reduction in carbon emissions by 2020. The principal renewable energy sources of Geothermal, Hydro-, Solar, Tidal and Wind are now being investigated worldwide with regard to their contribution towards a “greener planet.” Their economics and those for conventional electricity generation are usually compared in terms of a Levelized Cost which is the sum of those for capital investment, operation, maintenance and decommissioning using Net Present-day Values. Because some proposed systems are less well-developed for commercial application (i. e., riskier) than others, or are long term in the

Nuclear Electric Power: Safety, Operation, and Control Aspects, First Edition. J. Brian Knowles.

© 2014 John Wiley & Sons, Inc. Published 2014 by John Wiley & Sons, Inc.

sense of capitally intensive before any income accrues, the now necessary investment of private equity demands a matching cash return [52]. Also in this respect the electric power output from any generator has a degree of intermittency measured by

Capacity Factor

=(Annual Energy Output) / (Annual Output at Max. Power)

(1.1)

These aspects are included as discounted cash flows in a Capital Asset Pricing Model that assesses the commercial viability of a project with respect to its capital repayment period.

As well as satisfactory economics and environmental impact, a replacement commercial generator in a Grid system must provide its centrally scheduled contribution to the variable but largely predictable power demands on the network. Figure 1.1 illustrates such variable diurnal and seasonal demands in the United Kingdom. It is often

claimed in the popular media that a particular wind or solar installation can provide a specific fraction of the UK’s electrical energy demand (GWh), or service so many households. Often these energy statistics are based on unachievable continuous operation at maximum output and an inadequate instantaneous power of around 1V2kW per household.1 As explained in Section 3.3 it is crucial to maintain a close match between instantaneous power generated and that consumed: as otherwise area blackouts are inevitable. Moreover, because these renewables fail to deliver their quotas under not improbable weather conditions, addi­tional capital expenditure is necessary in the form of reliable backup stations. Assessments of the economics, reliability, Grid compatibility and environmental impacts of commercially sized generating sources now follow.