IMPACTOS DE LOS RESIDUOS SÓLIDOS SOBRE EL MEDIO AMBIENTE

Regarding DG, RES and storage systems, the technologies that have been considered are those, which can be applied at consumers’ premises and connected to low-voltage networks.

Analysed technologies include:

- Electricity generation technologies.

- Electrical energy storages.

- Heat/cool storages and solar heat connected to heat storages.

- Plug-in vehicles at consumers considered as electricity users, generators and storage.

3.5.1.1 DG and RES

Typically household cogeneration systems require high availability, often with periods of continuous operation, in order to be able to be considered useful. Factors such as malfunctions involving unforeseen maintenance costs reduce the advantages of such systems. Thus, while the CHP systems with internal combustion engines meet household’s needs and are already widely available on the market, with benefits and costs well-established, the micro-turbine systems and Stirling engines need further studies in order to make them more suitable for market’s requirements. The fuel cell systems are, however, in a large part, still at the prototype stage and have yet to complete testing on experimental facilities. On the other hand, with respect to their potential in terms of efficiency, noise and low emissions, the Stirling engine systems and Fuel Cell are considered the solutions of the future for domestic users.

The costs of these systems are indicative of their current trading condition, but the forecasts for the next five years show a significant reduction due to their entry to the mass markets.

It is possible for CHP systems to integrate active demand functions; however this is restricted due to several issues.

To obtain a so defined high efficient CHP system, the use of the produced heat is crucial. Also, generally, micro and small-scale CHP units show weak partial load efficiency. Both facts lead to base load role for CHP with between 4000 and 7000 operational hours per year. This results into a low level of active demand functions.

Compatibly with thermal production process constraints and with load reduction capability services can range from peak shaving to tertiary reserve and voltage regulation, up to support in islanded conditions.

ADDRESS Technical and Commercial Conceptual Architectures - Core document ADD-WP1-T1.5-DEL-EDF-D1.1-Technical_and_Commercial_Architectures

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Regarding generation systems from renewable energy sources (PV and Small Wind), it is evident that they are not dispatchable; their availability and flexibility is closely linked to the capability of coupling them with storage systems.

Current technologies do not generally allow generators based on renewable sources like sun or wind to deliver ancillary services. However, in the case of power electronic interface to the grid, a four- quadrant inverter could be adopted to contribute to voltage regulation and power quality in the distribution system.

Due to the strong stochastic nature of this type of renewable energy, integrating active demand functions is possible only in the cases in which energy storage is included.

Therefore heat and perhaps electricity storage becomes of higher importance for active demand function integration.

3.5.1.2 Status of energy storages at consumer level

Energy storages have a key role for an efficient distributed energy management. Most of the problems in power quality, distribution reliability and peak power management can be solved with energy storage devices. They give new possibilities for demand side management, and for consumer level energy cost control.

Cost effective, smart energy storages give potential for building energy management especially when they are used in combined heat and power (CHP) production systems such as fuel cells and micro turbines. Energy storages give also possibilities to manage uncontrollable power production in renewable energy generation systems such as photovoltaic and wind power systems. Finally, uninterruptible power delivery can be essential even in single family houses for example when they are used as a home office with computer systems or if they have critical medical equipment as may be more common in the near future.

Energy storage systems in residential applications include the storage systems that provide electric power output: electricity to electricity storages like capacitors or super-capacitors, mechanical power to electricity storages like flywheels, electrochemical storages such as batteries and flow batteries. Super (ultra) capacitors and flywheels can provide fast power response needed for distribution line stability and power quality (reactive power and voltage control, fault current limitation) support.

Flow batteries like vanadium redox batteries can fulfil variable power and energy demands.

Batteries, flywheels and capacitors are suitable for energy management, peak shaving and for mobile power applications.

Thermal energy storages are used in heating and cooling systems. Thermal energy can be stored as sensible heat, latent heat and chemical energy. They can also provide ancillary type reserve services for local and district thermal energy production systems. Advanced thermal energy systems for heating and cooling provide possibilities to integrate active demand functions.

The use of energy storages is pushed by increased demand for energy efficiency, reduction of CO2 and other emissions and increased exploitation of the renewable resources like solar power.

Anyway, most of the technologies in use today are still under intensive research and development. In the project a comparison between the various technologies was carried out in terms of the most important technological characteristics.

The comparison shows that each storage technology is different in terms of its network application, and energy storage scale. In order to achieve optimum results, the specifications of the storage device have to be studied accurately, before the final storage type selection.

ADDRESS Technical and Commercial Conceptual Architectures - Core document ADD-WP1-T1.5-DEL-EDF-D1.1-Technical_and_Commercial_Architectures

Revision 1.0

The current storage costs are still high. The electric energy lost in energy storage drives up the overall costs together with the required capital investment for the energy storage system. These costs will tend to decrease with increasing degree of market acceptance.

3.5.1.3 Plug-in Hybrid Vehicles as energy storage

The future perspectives of PHVEs are linked obviously to batteries development. At the moment, it seems that the best candidate for near future battery in electric vehicles is lithium battery.

A distributed storage system based on PHEVs would be available when their share is increasing: these storages can participate to active demand strategies and contribute to optimisation of production and utilization curves.

PV panels or other renewable sources based generation systems can be used to produce electric energy for PHE vehicles, instead of employing grounds for biomass growing for bio-fuels.