The conventional power grid is undergoing a radical transformation due to the evolution of distributed generation (DG). The formation of a microgrid is the most typical method of incorporating DG. A microgrid is a controllable entity composed of storage systems, conventional generators, DG sources and thermal and electrical loads that work together to bridge the supply-demand gap locally. District heating networks in industries need to be planned not just for the current energy system, but also for the one that will replace it. The term "smart energy system" is being used to describe such a system, which involves the integration of smart electrical, heat and gas networks that work together to maximize their potential.

The transition from the traditional energy system to the smart energy system

To make the switch from fossil fuels and nuclear power to more sustainable energy sources in the future, planners must include more and more intermittent renewable energy sources on a massive scale. Because of this, the current energy infrastructure must be rethought and redesigned. Integration of electricity, heating, cooling and transportation sectors, as well as utilization of demand flexibility and various forms of short-term and longer-term storage, are primary goals of smart energy systems. This is only possible through the smart energy system's ability to coordinate among the many smart grid infrastructures that make up the energy network, such as those grids that supply electricity and district heating and cooling, gas and various fuel systems.

Architectures of smart energy systems

There are three main grids that support the smart energy system:

• Smart electricity grids in which adaptable electrical loads, like those of heat pumps and electric vehicles (EVs), can be met by linking up with intermittent renewables like wind and solar power.
• Smart thermal grids connect the power and heating industries. By doing so, the energy system may make use of thermal storage to increase its adaptability and reduce wasteful heat loss.
• Smart gas grids that link the power, heating and transportation industries. This allows gas storage to be used to increase operational flexibility. As an added bonus, liquid fuel storage facilities can be put to use if the gas is converted to a liquid form.

What kinds of simulation and design tools are available for integrated grids?

The simulation and design of smart energy systems necessitate the use of tools and models that can be applied to the entire energy system, not just specific grids. To take into account seasonal fluctuations and accurately represent the use of storage, tools suitable for the simulation and design of smart energy systems need high temporal resolution and the ability to simulate seasonal fluctuations and accurately depict how storage is being used. Storage options representing various energy carriers, such as green gas, hydrogen and electricity must be included in any model or tool used to analyze energy storage. Tools and models should also be able to determine the states of storage in a time-stamped manner for each computation period.

[See also: Internet of energy: Shaping the future of smart grids]

Benefits of integrating electrical, thermal and gas grids

Smart energy systems are engineered to locate complementary features to arrive at the best possible optimal solution for each sector and the entire energy system. Examples of such improvements include:

• When compared to storing electricity, storing heat is both cheaper and more efficient. Combined heat and power production is also made more adaptable.
• District heating allows for the utilization of excess heat from other sources, such as the generation of electricity and industrial processes for heating buildings.
• District cooling networks can receive cooling from heat pumps and heat pumps can supply cooling for these systems.
• Power and electric grid services, such as load balancing and regulation of power markets, can benefit from the usage of electricity for heating.
• The process of transforming biomass into gas and liquid fuel requires steam, which may be generated at combined heat and power facilities, and results in low-temperature heat, which can be put to use by district heating and cooling networks.
• District heating may be a more cost-effective option than on-site generation of the low-temperature heat required for biogas production.
• Vehicle batteries may be charged using electricity, which can then be used to substitute for gasoline and help balance the grid.
• Space heating energy savings in buildings allow for the implementation of low-temperature district heating, which in turn allows for the utilization of improved low-temperature sources, such as industrial surplus heat and combined heat and power.
• Hydrogenation, an electricity-to-gas conversion process, allows for the use of gas storage in place of electricity storage, which is more cost-effective and energy-efficient.

Conclusion

In a nutshell, integrating thermal, electrical and gas grids offers the capability of achieving zero carbon dioxide emissions, zero reliance on imported energy and zero reliance on fossil fuels. Many of the technologies being used, particularly in the areas of energy and heat such as EVs, photovoltaic panels and thermal energy storage, have reached a point of maturity where they may be put into use immediately.