Environmental Engineering Reference
In-Depth Information
the inertia of the conventional power plant. An economic benefit from uncertainty predic-
tions can in the most static markets only be achieved, if the prediction ranges up to 48 hours
ahead. The trading of up-regulation and down-regulation can then be synchronised with the
trading of the total generation and therefore the handling costs of wind power on the grid
can be optimised.
This creates not only an economic advantage for the system operator, but also a fair
strategy for the intermittent energy source, as it prevents dominant generators with large
market shares gaining exclusive contracts caused by the imbalance from wind generation.
In addition to the economic benefit, there is a security benefit of trading reserve capacity in
advance, as the capacity can then be scheduled with the focus on grid security.
7.1.
Optimisation of Reserve Predictions: Example Denmark
Next an example of a reserve prediction scenario is presented, based on a situation in
which there is knowledge of the uncertainty of the wind power forecast in advance. This
assumption is reflected by the statistical scores.
The up-regulation and down-regulation has been counted separately, because of the
asymmetry in the market pricing structure. Note however, that for convenience, the compu-
tation of the
optimal forecast
in the example below is for simplicity based on the assumption
that the price of up-regulation and down-regulation is the same, which would normally not
be the case. It should in most cases be more efficient to trade with a lower prediction of
future production of wind power than expected and arrange for down-regulation, when the
wind power production increases above the predicted power, because down-regulation is in
many markets n average only 25% of the price for up-regulation.
In our example, we compared different forecasting scenarios:
1. Scenario: Use of the optimal forecast and reserve prediction for next day's wind
generation.
2. Scenario: Use of the optimal forecast for next day's wind generation, where reserve
is only allocated on the next day according to the demand.
3. Scenario: Use of the Ensemble average forecast for next day's wind generation,
where reserve is only allocated on the next day according to the demand.
The scenarios in this example were constructed for a fully competitive market, where
reserve capacity is traded day-ahead. In this example, we used the same single forecast in
both scenario no. 1 and no. 2. In scenario no. 1 we allocated reserve capacity in a market
with competition on reserve. In case no. 2 and no. 3 all regulation was traded according to
the demand on the short-term spot market.
Table 2 shows the results of the 3 scenarios. Note, that all values are in units percent
of installed capacity. The numbers are taken from prioritised production in the western part
of Denmark in the period January to April 2005. The forecast horizon is 17 to 41 hours
until daylight saving starts, then the forecast horizon changes to 16 to 40 hours. The total
prioritised production is rated at 1900 MW in this period, which is almost equivalent to the
minimum consumption in this area.
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