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Hedging Strategy and Electricity Contract Engineering - IFOR

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õ<br />

õ<br />

õ<br />

á<br />

á<br />

6.5 Analysis of optimal dispatch strategy 141<br />

õ<br />

ìj<br />

Wú ¦ bëi<br />

¦ bë j ì<br />

1<br />

¦ Û bë<br />

j<br />

bë j ì<br />

1 Ý Ü õ ìj ì<br />

1<br />

1 õ<br />

ìj<br />

Or else one pumping weight equals one, i. e. ìj<br />

1 for an 1Ü j<br />

<strong>and</strong> two adjacent production õ weights i õ 1 <strong>and</strong> õ ë<br />

i<br />

for an i 2Ü<br />

ë<br />

are non-zero <strong>and</strong> given by<br />

ì<br />

á@á?á<br />

Ükô<br />

r Ü<br />

á?á@á<br />

i ë<br />

¦ bë<br />

j bëi 1<br />

Wú ¦<br />

Ü ë<br />

bëi bëi 1<br />

ë<br />

i ë<br />

1<br />

1<br />

ì<br />

i ë<br />

The proposition is proven in Appendix A on page 197.<br />

To further exploit the production <strong>and</strong> pumping problem (6.26), we study the<br />

special case, ô where r <strong>and</strong> S 1 Së1<br />

ö<br />

áaá@á<br />

Sì1<br />

.<br />

Ü<br />

S Ü r Sì Sër<br />

Corollary 6.8<br />

The pumping decision is related to the production decision by the marginal<br />

value of water <strong>and</strong><br />

(i) Assume production at price S i , then the marginal value of water is u i .<br />

Pumping occurs below price S j j é iÝ , where the marginal value of<br />

Û<br />

water u j u è i u j 1.<br />

ë<br />

(ii) Assume pumping at price S j with marginal value of water u j . Then production<br />

occurs at price S i Û j é iÝ where è u i u j è u i<br />

ë 1.<br />

The corollary is proven in Appendix A on page 198.<br />

6.5.3. Conclusion <strong>and</strong> choice of exercise functions<br />

We have in this section, for the special case, where the probabilistic water constraints<br />

<strong>and</strong> the risk constraint are inactive, derived a number of results <strong>and</strong><br />

showed that step functions indeed are the correct exercise functions. In the<br />

general case, where risk <strong>and</strong> intermediate water level is of concern we can rely

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