Renewable Energy Systems and Models

This Topic page provides information on:

- Energy System Analysis tools for the design of Renewable Energy Systems

- Studies of large-scale integration of fluctuating Renewable Energy Sources

- Design of 100% Renewable Energy Systems

Renewable energy is defined as energy arising from natural resources such as sunlight, wind, rain, waves, tides and geothermal heat, which are naturally replenished within a time span of a few years. Renewable energy includes the technologies which convert natural resources into useful energy services:

- Wind, wave, tidal and hydro power (incl. micro and river-off hydro)

- Solar power (incl. photo voltaic), solar thermal and geothermal

- Biomass and biofuel technologies (including biogas)

- Renewable fraction of waste (household and industrial waste)

Renewable Energy Systems are defined as complete energy supply and demand systems based on renewable energy as opposed to nuclear and fossil fuels. Renewable Energy Systems include supply as well as demand. The transition from traditional nuclear and fossil fuel-based systems to Renewable Energy Systems involves coordinated changes in:

- Demand technologies related to energy savings and conservation

- Efficiency improvements in the supply system such as CHP

- Integration of fluctuating renewable energy sources such as wind power

Additional to the above-mentioned renewable energy technologies, Renewable Energy Systems include both technologies which can convert from one form of energy into another, such as e.g. electricity converting into hydrogen, as well as storage technologies which can save energy from one hour to another.

The large-scale integration of renewable energy sources into existing energy systems must meet the challenge of coordinating fluctuating and intermittent renewable energy productions with the rest of the energy system. Especially with regard to electricity production, meeting this challenge is essential since electricity systems depend on an exact balance between demand and supply at any time.

Given the nature of photovoltaic (PV), wind, wave and tidal power, only little can be gained by regulating the renewable source itself. Large hydropower producers make up an exception, since such units are typically well suited for electricity balancing. The possibilities of achieving a suitable integration are to be found within the surrounding system, i.e. the power and CHP stations which constitute the rest of the supply system. The regulation in supply may be facilitated by flexible demands, such as e.g. heat pumps, consumers’ demand, and electric boilers. Moreover, the integration can be helped by different energy storage technologies.

The implementation of 100 per cent renewable energy systems adds to the challenge of integrating RES into existing energy systems on the large scale.

The design of suitable energy systems has to consider both conversion and storage technologies. Renewable energy will have to be compared not to nuclear or fossil fuels but to other sorts of Renewable Energy System technologies, including conservation, efficiency improvements and storage and conversion technologies; e.g. wind turbines versus the need for biomass resources. The influence of each technology on the system is complex, not only with regard to differences in hourly distributions but also in terms of identifying a suitable combination of changes in conversion and storage technologies.

On a global scale, a large number of different computer models exist which can all be called energy system analysis models in the sense that they make calculations related to the analysis of energy systems. However, in the analysis of large-scale integration of renewable energy as well as in the design of 100% renewable energy systems, it becomes essential to make hour-by-hour calculations due to the fluctuations in most renewable energy sources. And it also becomes essential to include proper analyses of advanced conversion and storage technologies in the system. One of model which can help in the making of such analyses are the EnergyPLAN model, which can be assessed from the homepage: www.EnergyPLAN.eu.

Ireland: EnergyPLAN has been used to create a model of the energy system in the Republic of Ireland. This model simulates the electricity, heat, and transport sectors so that alternative energy scenarios can be developed for Ireland moving forward towards 2020 and beyond. To date, the reference model has been created based on actual consumption and production from the year 2007. After creating the model, a comparison was made between the actual figures and those simulated by EnergyPLAN. It was concluded that EnergyPLAN could simulate the Irish energy system accurately, as the largest difference identified between the actual figures and the model was approximately 2%. Therefore, this model was subsequently used to analyse the future energy costs on the Irish energy system if a business-as-usual scenario was followed and also, to analyse the maximum wind penetration feasible on the Irish energy system. These analyses found that the energy costs in Ireland could increase by up 50% in 2020, due to a large dependence on imported fossil fuels and also, the maximum wind penetration feasible on the current Irish energy system (i.e. without any changes) is approximately 30%. A full overview of this study can be found at: www.dconnolly.net.