Wind Turbines and Capacity Credit

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There are a great many terms used to describe and define the energy produced by wind turbines. The term of most interest to me is that of the "Capacity Credit".

Capacity Credit can be defined as either:

Where turbines postpone the need to install other new generating capacity, after new consumers have been given access to the grid, they may be paid a certain amount per year as a capacity credit.

Or:

The capacity credit of wind power expresses how much ‘conventional’ power can be avoided or replaced by wind power.

These techniques are used for estimating the social benefit of large-scale wind power installations.

The social benefit is based upon wind power's energy and capacity services and the avoidance of environmental damages. The approach uses probabilistic load duration curves to account for the stochastic interaction between wind power availability, electricity demand, and conventional generator dispatch.

If natural gas combined cycle and integrated gasifier combined cycle (IGCC) are the alternative generation sources, wind power exhibits a negative social benefit due to its high capacity cost and the relatively low emissions of these advanced fossil-fuel technologies.

Environmental benefits increase significantly if charges for CO₂ emissions are included. Results also reveal a diminishing social benefit as wind power penetration increases.

The methodology is intended for use by energy planners in assessing the social benefit of future investments in wind power.

I am interested in the latter definition and believe an assessment of capacity credit should be done for each proposed turbine facility. These assessments will help to ensure that the installation is beneficial and provides a positive social benefit, to offset the negative social and environmental impacts.

The danger with the Victorian grid, which provides its base load via brown coal burners, is that if these developments are poorly managed, we will only obtain an 8% offset in power generated by other sources (an 8% capacity credit).

The figure of 8% relates to the firm contribution, planned reduction in demand or contribution to system reserves.

This is the amount that generators can rely upon to reduce the base load power, ie: brown coal generation in Victoria.

The remaining 22% (if 30% is the actual output) is used to energise the grid and hopefully fast reactor gas fired units or hydro power can make use of it.

If the mechanisms are not in place to maximise the use of the remaining 22%, then the only benefit that we receive, for the 30% of payments, will be the 8% reduction in baseload.

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