Stages of technological maturity of renewable energy
Source: UNEP 
Renewable energy Research and development stage Demonstration and deployment stage Diffusion stage Commercial maturity stage
- Hydrokinetic turbines - Run-of-river
Aquatic plant-derived fuels Pyrolysis-based biofuels
Lignocellulose sugar-based biofuels
Lignocellulose syngas-based biofuels
Combined heat and power
Co-firing fossil fuels
Sugar and starch-based ethanol
Plant and seed oil-based biodiesel
Higher-altitude wind generator
Offshore, large turbines
Onshore, large turbines
Distributed, small turbines
Turbines for water pumping
Concentrating solar thermal power
Low temp solar thermal
Passive solar architecture
Submarine geothermal energy
Engineered geothermal systems
- Direct use applications
Geothermal heat pumps
Hydrothermal, binary cycle
Hydrothermal, condensing flash
Ocean thermal energy conversion - Tidal range
However, using renewable energy is challenging because it has some very serious drawbacks, among which we can mention the following:
- Intermittent nature of renewable sources (such as wind and photovoltaic), which can lead to system imbalances . The capacity of renewable energy has to be integrated into the energy system by the grid operators, but the system planning and the investments needed are hindered by the intermit...
... middle of paper ...
...ified through the role played by public power, that is the role of protecting the citizen, especially in two respects: the right to receive the requested service and the right to equitable tariff. It is widely accepted that there may be a public service if a community (local, regional, national, European) estimates that at some point, within the area of responsibility, a good or an essential service for all, existing or new, cannot be satisfactorily provided only through market mechanisms [27–29].
There is a need for a new attitude in both design and management of modern services in order to develop renewable energy in the European Union. Moreover, in this context, the role of the state and the services it provides in ensuring energy security, as well as in establishing energy policy will continue to be important, and will be intensified in some areas of action .