Optimal Design of a Hybrid Solar-Wind Energy System with Pumped Hydro Storage for Stand Alone Power System Considering Expected Energy Not Supplied

Abstract

This paper proposes the algorithm for optimal design of a stand-alone power
system consisting of wind, PV and pumped hydro storage, taking into consideration the
expected energy not supplied. The algorithm consists of two stages which employ the
same problem formulation. The problem formulation uses the capital costs of the standalone
power system together with the cost of expected energy not supplied as an objective
function. The constraint functions consist of load profiles of medium general service from
Provincial Electricity Authority (PEA), the statistical forecasting data of wind and solar
energy, and the operation of pumped hydro storage system. The calculation in the first
stage ensures that there is no expected energy not supplied. The optimal results with
zero load shedding from the first stage yield the number of PV units, the number of wind
turbines, the rated capacity of pump motor and hydro turbine, and the maximum volume
of the upper reservoir for storage system. Then these optimal results are fed back into
the formulation as fixed parameters in the second stage calculation. The calculation is
done on the system with various probabilities of solar and wind energy in order to obtain
the minimum costs of load shedding when shortage of wind and solar energy should occur.
The results of the second stage show the operating cycles of pump and hydro turbine,
and the changed volumes of water in the reservoir in all considered periods. The results
from both stages of the algorithm show the additional costs of energy not supplied when
the probabilistic values of renewable energy are taking into consideration in the optimal
design of the stand-alone system.