Aim of a hybrid power plant
A hybrid power plant aims to cover without interruptions and according to the pre-defined qualitative requirements a specific power demand, based on non-guaranteed power production plants.
To achieve this aim, it is necessary to support the non-guaranteed power plant with a storage plant (or more than one).
In any occasion, to guarantee secure energy production, the hybrid power plant is integrated with a guaranteed power production unit, as a back-up unit.
Consequently, according to the above mentioned, a hybrid power plants consists of the following discrete components:
- non guaranteed power production plants (base units)
- storage power plants
- guaranteed power production units (back-up units).
Hybrid power plants applications
Hybrid power plants are mainly developed for the production of:
- thermal energy.
The following parameters:
- whether the hybrid power plant is developed in an interconnected or in an autonomous grid
- the size of the hosting grid
- the size and the components’ type of the hybrid power plant
determine whether the hybrid power plant should be designed for:
- the power demand peak shaving, aiming primarily to the reduction of the energy production specific cost
- the maximisation of the energy production from the hybrid power plant, aiming at the 100% cover of the annual energy consumption.
The base units of a hybrid power plant
The base units of a hybrid power plant are the non-guaranteed power production ones.
They are characterized as “base units” because of the fact that the power production from the hybrid power plant is mainly based on them, namely they are the basic production units.
The base units of a hybrid power plants exhibit absolute priority regarding their dispatch order. The main objective of the hybrid power plant is the maximization of the exploitation of the non-guaranteed energy produced by the base units.
In an electricity production hybrid power plant the base units can usually be:
- wind parks or small wind turbines
- photovoltaic stations.
In a thermal energy production hybrid power plant the base units can usually be:
- solar collectors (flat, of selective coat or concentrated).
The storage units of a hybrid power plant
The storage units of a hybrid power plant aim, through the bidirectional power flow from and to it, to adapt the non-guaranteed power production from the base units, determined by the availability of the employed Renewable Energy Sources (R.E.S.) technology, to the inelastic power demand.
The storage units do not produce power from a primary energy source. On the contrary, they store the available energy from the base units, which, for several reasons, can not penetrate directly to the grid, and returns it to the consumption usually in a different time point.
In an electricity production hybrid power plant, the storage unit can be:
- electrochemical batteries of several types, depending on the size of the hybrid power plant
- fuel cells co-operating with hydrogen production electrolysis units
- pumped hydro storage systems
- compressed air energy storage systems.
In a thermal energy production hybrid power plant, the storage unit can be:
- storage water tanks
- rock beds.
The back-up units of a hybrid power plant
The back-up units of a hybrid power plant aim to the cover of the power demand with guaranteed power production in cases the base or the storage units are not able to provide enough power (low availability of R.E.S. potential and simultaneous low charge level of the storage units).
The back-up units exhibit ultimate priority, namely they are dispatched last in the power production, only once there no possibilities production from the alternative base or storage units.
The effective dimensioning of a hybrid power plant, optimized with energy criteria, aims to minimize the energy production from the back-up units over an overall time period.
In an electricity production hybrid power plant, the back-up units can be:
- diesel generators of large or small size, depending on the size of the hybrid power plant
- fuel cells, on the condition that the availability of the consumed fuel can be considered as guaranteed.
In a thermal energy production hybrid power plant, the back-up units can be:
- conventional oil or biomass heaters
- heat pumps.