UE 13: Sector integration Flashcards
Name flexibility options for the integration of renewable energies.
Efficient grids
- Electricity grids: Grid optimization, reinforcement and expansion
- Coupling with gas grids and heat grids in the context of sector coupling
- Imports/exports
Flexible consumers/Demand side management
- Load management in industry, service sector and households (especially electric heat pumps and electric vehicles)
- Power-to-heat as a sector coupling technology
Storages
- Electricity storage
–> Pumped storage
–> Compressed air storage
–> Battery storage/accumulators - Heat & gas storage
–> Power-to-gas/power-to-liquids as a sector coupling technology
–> Expansion of heat storage/gas storage for flexibilization of CHP or power-to-heat
Flexible producers
- (Controllable) renewable energies
–> Flexible use of biomass and biogas
–> Grid- or market-induced curtailment of wind and photovoltaics - Retro-fitted carbon neutral power plants
–> Transition: Retro-fitted existing (gas fired) power plants, CCS
–> Electricity-led use of CHP depending on electricity prices
–> New construction of flexible (hydrogen-fired) power plants
What is missing?
Flexibility Options for the Integration of Renewable Energies
- “…” in generation and consumption
- “…” in energy transport
- Goal: integration of renewable energies
“Temporal flexibility”
“Spatial flexibility”
What is missing?
Flexibility options: grid expansion
- Goal: Overcoming “…”
“spatial discrepancies/providing spatial flexibility”
What is missing?
Flexibility options: storages
- Goal: Overcoming “…”
“temporal discrepancy/providing temporal flexibility”
Provide the actual technologies behind:
1) Power-to-Heat
2) Power-to-Mobility
3) Power-to-Gas
4) Power-to-Liquids
5) Hydrogen-to-Heat
6) Hydrogen-to-Mobility
7) Hydrogen-to-Electricity
1) Power-to-Heat
- Heat pump
- Electrode boiler
2) Power-to-Mobility
- Electric Motors and batteries
3) Power-to-Gas
- Electrolysis
- Pyrolysis
4) Power-to-Liquids
- PtG + Fischer–Tropsch process
5) Hydrogen-to-Heat
- H2 gas heater
- H2 CHP
6) Hydrogen-to-Mobility
- Electromobility fuel cell
- Synthetic fuels
7) Hydrogen-to-Electricity
- Fuel cell
- H2 gas turbine
- H2 CHP
What are the advantages of sector coupling/integration?
Improved energy efficiency
- E.g. waste heat from industry can be used to heat buildings (e.g., district heating)
- E.g. using electricity directly in heating and transport (e.g., heat pumps, electric vehicles) increases the energy efficiency
Integration of renewables into energy system
- E.g. avoiding curtailment by using surplus power (through flexible consumers (e.g. PtG))
Increasing flexibility and grid stability
- E.g. flexible consumers curb/delay demand in times of a high residual load and increases demand in times of a negative residual load
- E.g. grid expansion enabling more options to balance supply and demand
Decarbonization of hard-to-abate sectors
- Green hydrogen or synthetic fuels made from renewable electricity can decarbonize sectors like steel, aviation, or shipping.
True or false?
Power-to-Heat: Converting Power (Surpluses) into Heat and Replacing Fossil Fuels
- In principle, both space heat and process heat can be generated by power-to-heat.
- Space heating can be generated decentrally (at the customer) OR generated centrally and then distributed via district heating.
- There are several technologies available for process heat, but often processes must be adapted to switch from conventional to electric heating.
–> Not all processes can be switched to electric heating (e.g. temperature level requirements, need for carbon).
–> Adjustments to processes often lead to pauses in production and are therefore only possible when major revisions are due anyway.
True!
Power-to-Heat: Converting Power (Surpluses) into Heat and Replacing Fossil Fuels
Name the most relevant PtH technologies providing space and process heat.
Power-to-heat
Space heat
- Central
–> District heating
–> Industrial heat pumps - Decentral
–> Heat pumps
Process heat
- Induction heating
- Conductive heating
Name the different types of storages, the type of energy they store and provide an example for each.
Electrical storage
- Electrical energy
- E.g. capacitor, inductor
Chemical storage
- Chemical energy
- E.g. hydrocarbons
Electro-chemical storages
- Electro-chemical energy
- E.g. batteries
Mechanical storages
- Kinetic or potential energy
- E.g. pump hydro storages, compressed air reservoir
Thermal storages
- Thermal energy (heat + coldness)
- E.g. latent or sensible heat storages
True or false?
Stored Hydrogen Can Be Utilized to Generate Electricity Using Fuel Cells Or Gas Turbines
- Fuel cells convert chemical energy directly into electrical energy by the reverse process to that of electrolysis.
- Hydrogen can be used in combustion turbines.
- Fuel cells and combustion turbines are not competing for the same applications. Fuel cells are much more suited to decentralized designs (e.g., for powering cars), whereas turbines are more suited for large-scale centralized requirements.
True!
True or false?
Re-electrification of H2
- Hydrogen conversion into electricity has poor energy efficiency, ranging from 30% to 60%, according to the technology used (fuel cells or turbines).
- Combined with the energy penalty from using electrolyzers, these re-electrification losses result in a round-trip efficiency ranging from 20% to, at best, 48%, if technology develops as expected.
- In order to compete directly with other electricity storage solutions, the efficiency penalty needs to be compensated for by hydrogen’s unique ability to store energy.
True!
True or false?
Re-electrification of H2
- Recovering heat losses from re-electrification is essential to improve the energy efficiency of the system and lower the levelized cost of electricity delivered.
- Heat losses could be recycled in two ways:
1) for heating purposes, within combined heat and power [CHP] applications. Heat is very hard to transport over long distances, which is why micro-CHP fuel-cell systems for decentralized applications are an important part of today’s fuel-cell-system installation. The energy efficiency of hydrogen-to-CHP should be able to reach 75%
2) conversion into electricity in a combined-cycle power plant to increase the electricity efficiency of continuous operations. High-temperature waste heat and a large-scale system are required to compensate for increased capital costs, limiting this application to gas turbines or high- temperature fuel cells
True!
True or false?
Re-electrification of H2
- Fuel cells and combustion turbines do not compete directly for the same application
- Fuel cells prioritize reliability/autonomy/low maintenance (e.g., back-up systems, uninterrupted power supply) over the expense of capital costs per kW
- H2 turbines will be stationary and not smaller than ~10 MW. That contrasts with highly modular fuel cells
True!
True or false?
Re-electrification of H2
- Five different types of fuel cells have been developed, grouped into low- and high-temperature categories:
–> The hydrogen-to-electricity efficiency of low-temperature fuel cells (of which proton exchange membrane [PEM] is the most promising) is limited to 32% at present. The PEM fuel cell is the only candidate for mobility and has always been the most manufactured fuel-cell type. It is also “fit” for stationary applications, and a popular choice for grid-control services because of its reactivity
–> High-temperature fuel cells are generally more efficient (up to 50%), and well suited to stationary CHP systems of megawatt scale. They are commercially available with decent lifetimes (unlike high-temperature electrolyzers) but remain very expensive to manufacture. Solid-oxide fuel cells are particularly promising as they can easily be reversed to become electrolyzers and can be operated using H2, syngas, methane or methanol.
True!
True or false?
Re-electrification of H2
- Gas turbines can also be used to burn hydrogen; the hydrogen can be pure or mixed with natural gas or syngas.
- Flexible syngas turbines are able to operate with an undifferentiated mix of H2 and CO with up to 70% hydrogen in mass. They have recently been commercialized for coal-gasification power plants
- 100%-hydrogen turbines remain in the early demonstration phase because of limited demand but would pose only moderate technical issues. Slightly different turbine designs are necessary to cope with the specificities of hydrogen, but the components of the plant would remain quite similar.
True!
True or false?
Possible Energy Supply per Mode of Transport
- If intelligently integrated into the energy supply system, electric mobility can make an important contribution to the storage of renewable energies. A particular challenge here is the increased load on the grid.
- Power-to-Fuels: In addition to the direct use of electricity as an energy source in road traffic, there is also the possibility of storing electricity in the form of chemical energy and thus using it as fuel in the transport sector.
- Biofuels (biodiesel, bioethanol, biogas) can also make a limited contribution. However, the conflict of land use must be considered here.
True!
What is missing?
Storages are a critical component due to the different energy density of the stored fuels.
Compared to fossil fuels, electricity and hydrogen have disadvantages with regards to “…”.
“volume or weight of the storage”
