Renewable Energy Sources for the mCCHP-SE-RES Systems - Design for Micro-Combined Cooling, Heating and Power Systems - page 100

Fig. 7 Available energy storage technologies ( € /kW) [ 11 ]

There is no single energy storage option to cover all requirements. Applications,
technological development, and market evolution will de ne the share of decen-

tralized storage solutions of the electrical energy.
The PV and daily storage is well suited for PV peak generation. This is because
it is guaranteed that PV generation is available every day with a perfectly pre-
dictable peak that always occurs around midday. As the peak demand in house
occurs in the evening hours the time shift between peak PV generation and the peak
demand never exceeds 8 h.
Batteries are integrated into the classical power conversion systems with the
purpose of providing additional energy as required by the load. The battery (sec-
ondary generation) is rechargeable by basic chemical reaction reversibility.
Autonomous power systems supplied by RES need energy storage for their oper-
ation. Traditional energy storage system is lead-acid batteries. In addition to the
storage device itself, a variety of energy management components are required, for
example the charge controller. Storing energy produced by RES is dependent on the
state of battery charge. If the battery is charged, RES energy production is not used.
In addition, storage energy in batteries can be made only in the short term. There is
no technology to long-term energy storage in batteries.
Weekly and seasonal storage capacities can be achieved by hydrogen technol-
ogy. Hydrogen is not a primary energy source like coal and gas. It is a clean energy
carrier with the unequaled advantage of being storable in various forms and
transportable in various modes. For instance, compressed at 700 bar, H 2 is well over
100 times more energy dense than a Li-ion battery (33 kWh/kg for H 2 vs. 0.2 kWh/
kg for battery). Hydrogen can be produced from carbon-free or carbon-neutral RES
by electrolysis. The hydrogen production can be made using electrolysers powered
by PV panels. The hydrogen produced by the electrolyser during summer provides
the necessary stock for the fuel cell to function the longest period of time possible,
in winter. Using fuel cell — hydrogen technology, the hydrogen and electricity are