THE PURPOSE OF THIS PROJECT IS TO CONDUCT A TECHNICAL/ECONOMIC STUDY OF A COMBINED HYDROELECTRIC/PHOTOVOLTAIC POWER PLANT FOR A REGION WITH SUFFICIENT WATER SUPPLY IN THE WINTER MONTHS AND A SCARCE WATER SUPPLY TOGETHER WITH HIGH SOLAR ENERGY DURING THE SUMMER MONTHS.
The use of a photovoltaic power plant in combination with a hydroelectric power plant conserves water in the reservoir when the photovoltaic plant is in use, in the sunny dry season. This is analogous to pumped water storage but much more efficient since no water is actually pumped up to the reservoir.
The plant concept defined was a 1 MW photovoltaic array inverter system, tied directly to the low voltage transmission network, incorporating low cost array structures, a reliable monitoring system and solar sensors. Array costs were kept low by using a low tilt angle and a longer panel length in a fixed tilted flat plate array.
Other key results of the study were as follows:
a photovoltaic inverter system with no batteries, directly tied to the local network served by a small hydroelectric plant, can be very effective;
the estimated alternating current energy output of the plant, at a site near Toledo, was 1520 MWhours;
no advanced new technologies are required to implement the plant design.
ONE SET OF OPERATIONAL SCENARIO IS TO 1) INSTALL THE PV PLANT IN THE CENTRAL SPANISH HIGH-LAND, IN THE NEIGHBOURHOOD OF ALREADY EXISTING MEDIUM-CAPACITY WATER RESERVOIRS. THE PLANT WILL GENERATE ENERGY FOR REMOTE VILLAGES IN A COMBINED, REGULATED USE OF HYDROELECTRIC ENERGY AND THE STORAGE CAPACITY OF THE WATER RESERVOIRS WHILE EXTRACTING THE MOST ENERGY FROM THE PV ARRAY, AND 2) USE OF WATER IN THE RESERVOIR AS ENERGY STORAGE MEDIUM. SOME OF TE HYDROELECTRIC POWER PLANTS PHYSICALLY SHUTS DOWN OR SLOW DOWN THE POWER DISPATCHING DUE TO LACK OF WATER LEVEL IN THE RESERVOIR GOES BELOW A THRESHOLD IN THE SUMMER MONTHS. ON THE OTHER HAND, THE SOLAR ENERGY IS HIGHER DURING THE SUMMER MONTHS, THUS THE PV POWER PLANT DEFINITELY COMPLEMENTS THE OUTPUT OF THE HYDROELECTRIC PLANT THROUGHOUT THE YEAR. THEREFORE, THE USE OF THE WATER RESERVOIR AS AN INDIRECT ENERGY STORAGE ELEMENT FOR THE PV PLANT WITHOUT PUMPING WATER UP TO THE RESERVOIR INHERENTLY LEADS TO A VERY HIGH OVERALL EFFICIENCY AND IS VERY ATTRACTIVE.
THE RESULTING PV PLANT CONFIGURATION IS A PV/INVERTER SYSTEM TIED DIRECTLY TO THE LOW-VOLTAGE TRANSMISSION NETWORK, USE OF MODULAR, RELIABLE DAS AND SENSORS DEVELOPED IN DG XII CONCERTED ACTION TASK, INCLUDING IMPROVED REAL-TIME ANALYSIS TECHNIQUES, AND A FIXED TILTED PV ARRAY. IMPORTANT NEW IDEAS TO REDUCE ARRAY COST ARE LOW-TILT ANGLE AND A LONGER PANEL LENGTH LIKE A ROOF-TYPE DESIGN BUT GROUND MOUNTED.