Renewable Energy Systems

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

• 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

A distinction can be made between end use and demand. Energy end use is defined as the human call for energy services such as room temperature, transportation, and light. Energy demand is defined as consumer demands for heat, electricity, and fuel. Consumers include households and industry as well as public and private service sectors. Fuel may be used for heating or transport. Heat demand may be divided into different temperature levels such as district heating and process heating.

Within end use, one may distinguish further between, on the one hand, basic needs such as food, basic temperatures, and transportation from home to work and, on the other, specific requirements such as a certain number of square meters with a certain room temperature and a certain number of kilometers of driving. This distinction can be critical for example, when analyzing the transportation infrastructure related to food production or to transportation between home and work. However, in the analyses presented in this book, it has not been necessary to make such a distinction.

Changes such as insulation and efficiency improvements of electric devices leading to changes in the energy demand for heat, electricity, or fuel are defined as changes in the demand system. In addition to the preceding renewable energy technologies, renewable energy systems include both technologies, which can convert from one form of energy into another for example, electricity into hydrogen as well as storage technologies that can save energy from one hour to another. Mathiesen (Mathiesen and Lund 2009) and Blarke (Blarke and Lund 2008) comprise these technologies under the designation relocation technologies. However, in the following, the difference between energy conversion and energy storage technologies is emphasized.

Energy conversion technologies are technologies that can convert from one demand (heat, electricity, or fuel) to another, such as the following:

• Conversion of fuel into heat and/or electricity by the use of technologies such as power stations, boilers, and CHP (including steam turbines as well as fuel cells)

• Conversion of electricity into heat by the use of technologies such as electric boilers and heat pumps

• Conversion of solid fuels into gas or liquid fuel by the use of technologies such as electrolyzers and biogas and biofuel plants

Energy storage technologies are defined as technologies that can store various forms of energy from one hour to another, such as the following:

• Fuel, heat, and electricity storage technologies

• Compressed Air Energy Storage (CAES)

• Hydrogen storage technologies

Keep in mind that the definition of storage technologies is broader than the concept of storage itself. For example, in the case of electricity, which is stored by converting it into hydrogen, the storage technology may include conversion technologies such as electrolyzers and fuel cells. The distinction between conversion and storage technologies is defined by the purpose of the technology in question. If the purpose is to convert electricity to hydrogen because a car needs hydrogen, then the electrolyzer is defined as a conversion technology. However, if the purpose is to store electricity, then the combination of electrolyzer, hydrogen storage, and fuel cell is defined as a storage technology.

In complex renewable energy systems, single components may be used for both purposes. For instance, the same electrolyzer may be used to supply cars with hydrogen and at the same time produce hydrogen for storage purposes. In this case, the electrolyzer is simply regarded as both a conversion and a storage technology.

The distinction between the two types of technologies is important when designing renewable energy systems, as will be elaborated on in Chapters 4 to 6. It is important to distinguish between, on the one hand, the need for balancing time and, on the other, the need for balancing the annual amounts of different types of energy demands.

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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