"Understanding the Future of Sustainable
Energy"
Future Grid of 2060
The future grid of 2060 integrates energy and transportation resources through a smart grid to supply electricity in an environmentally sensitive and reliable fashion from nationally secured energy sources.
The vision is novel as it addresses the major energy challenges including:
 | Global climate change |
| National security |
| Energy efficiency |
| Energy reliability |
| Heating |
| Transportation |
| Economic competitiveness |
Electrical energy is provided from renewable generation including wind, solar thermal, solar photovoltaic, hydro, geothermal and tidal energy; integrated gasifier combine cycle (IGCC) power plants with carbon capture and sequestration, as well as hydrogen co-production, combined heat and power plants, and nuclear power. Transportation is powered by both electricity and hydrogen on land. Electric transportation includes both battery electric technologies as well as direct electric transportation. Heating is based on solar heating and heat recovery from distributed generation of carbon neutral fuels including both biogas and hydrogen from coal plants with carbon capture and sequestration.
The grid of the future must be as efficient as possible to make the most of diminishing and limited resources, must be carbon neutral to avoid global climate change, and must be diverse in nationally secured energy resources.
Global climate change:
The future energy grid is based on carbon free technologies including renewable wind, solar, biomass, geothermal, and tidal resources and nuclear generation. Coal is used with high carbon capture and sequestration. Transportation is based on the carbon neutral electricity and hydrogen produced from coal implementing carbon capture and sequestration. Heating is based on solar heating and waste heat recovery from distributed generators operating on carbon neutral fuels.
National security
Electricity, transportation and heating are all based on resources available within the country. Solar, wind, biomass, geothermal and tidal energy are all renewable. Coal and uranium are both available domestically. Transportation is based on the electricity generated from domestically available resources and hydrogen from coal.
Energy efficiency
To maximize efficiency, future energy strategies need to reduce the number of energy conversion steps, rely on the most effective conversion approaches, and utilize heat recovery. Generated electricity needs to be used directly, thus avoiding unnecessary energy conversion steps leading to losses in energy. This means that energy storage should be avoided.
Coal is a largely available resource in the U.S . Because coal is carbon intensive by nature, the carbon must be separated and sequestered. Separating the carbon from coal is very energy intensive and can require high temperature and thermal energy depending on the processes used. To achieve highest possible efficiencies gasification should be integrated with electric generation where the heat for gasification and electric generation can be synergistically integrated.
To increase fuel conversion efficiencies of hydrogen and biogas, combined heat and power should be used to recover as much of the waste heat as possible. Combine heat and power makes it possible to utilize low quality heat that is not possible in thermodynamic cycles. This brings the important point that while coal gasification plants need to be integrated with some electric generation for synergistic heat integration, it maybe an efficiency benefit to transport part of the processed coal as hydrogen to distributed generators with waste heat recovery.
To increase fuel to electric efficiencies in combined heat and power and IGCC plants, fuel cell gas turbine hybrid systems can be utilize with demonstrated 65% plus fuel to electric efficiencies even at the small scale. The high efficiency at the small scale makes fuel cells very suitable for combined heat and power where the waste heat can be used locally and does not need to be transported long distances.
For transportation direct electric transportation from locally generated electricity should be used when ever possible. Biogas and hydrogen should be converted to electricity in combine heat and power plants where the waste heat can be recovered. The electricity can then be directly used in trains and busses without the need to carry fuel onboard the vehicles further increasing the efficiency. Where direct electric conversion is not possible, battery electric transportation where 85% plus of the electricity can be recovered should be utilized. If possible electric generation of hydrogen should be avoided as the conversion of electricity to hydrogen is about 80% and the conversion from hydrogen to electricity is 60% at best, resulting in round trip efficiency less then 50%.
Energy reliability
For stable grid operation, the amount of power generation onto the grid must equal the amount of electric demand. Generating power to match load demands gets more challenging with increased intermittent renewable generation. The easy solution is to use energy storage to aid in balancing the energy on the grid. However, storage is expensive and inefficient. To maintain grid stability with minimal amount of energy resources energy resources such as battery electric vehicles, combined heat and power plants, and cooling demands can be managed. Deploying energy resources to support the grid requires smart grid technologies where distributed energy resources communicate with the grid to such that the distributed energy resources can be optimally deployed to support the grid.
Smart grid technologies further make it possible to sense and respond to grid events automatically. Combined heat and power plants, wind turbines, and photovoltaic cells on top of roof tops generate diversification and redundancy in energy technologies increasing overall reliability. Solar, wind, hydro, biomass, and coal helps to diversify energy resources avoiding dependency on a single or few energy resource again creating energy reliability. To increase reliability it is further possible to implement large hydro-storage capabilities in case of emergencies.
Heating
It is easy to forget about heating as a major energy requirement in future energy outlooks. However heating is a critical aspect of energy utilization. Heating is addressed here by solar heating, combine heat and power and if necessary biogas or hydrogen combustion. However, it is always more efficient to meet heat demands by recovering waste heat from generators and to avoid burning fuel directly for heat. Fuel has the potential to make electricity, while waste heat does not. Hence to make the most of the fuel available, electricity should be generated from fuel and the waste heat generated in the conversion of fuel to electricity used to meet heating demands.
Transportation
Alternative modes of transportation are challenging because petroleum is a liquid with high energy density. The high energy density of petroleum makes it possible for vehicles to go long ranges without refueling. The liquid aspect of petroleum makes it possible to refill vehicles rapidly and is convenient for transportation. Transportation has emerged from human power, wind (sailing), to steam generators, to the petroleum we use today. The energy density of fuel keeps increasing.
Energy density is critical because fuel must generally be carried on board. Hence, the more energy dense the fuel the better suited it is for transportation. In direct electric transportation vehicles connect to an electrified rail or overheat wire for energy. In such scenario, no fuel is carried onboard and the energy density could be thought as being infinite. Such alternative follows the trend to increasing energy density transportation alternatives. In addition, direct electric transportation is powered from electricity that can be generated from renewable resources, or coal.
Direct electric transportation should be used whenever possible. Trains and busses that follow daily routes should be operated from electricity directly. Ideally, personal vehicles would connect to the grid but this may not be feasible without a major infrastructure investment. In the case that such an infrastructure does not immerge, battery electric transportation allows for flexibility in primary energy resources. However, without serious technological advancements battery technologies tend to be rather low in energy density and have limited range. For cases where extra range is necessary hydrogen vehicles seem attractive. Hydrogen has a very high energy density per mass but a rather low energy density per volume. Coal derived hydrogen vehicles can be attractive for future transportation.
For air and sea transportation where direct electric transportation is not feasible and the range of transport is critical, synthesis liquid fuels may have to be used. If such fuels are generated from coal some carbon dioxide emissions will result. Synthesis fuels such as bio-diesel that can be generated from biomass to avoid carbon dioxide emissions into the atmosphere.
Hydrogen and electric vehicles are both attractive transportation alternatives for land application. Electric transportation is the most attractive transportation alternative from an efficiency stand point. If hydrogen is available for transportation it is generally more attractive to use the hydrogen in a combined heat and power plant to generate electricity. In such a case, hydrogen to electric conversion maybe 60% with 50% of the waste heat recovered as useful energy for a total efficiency of 80%. The electricity can then be used in the vehicle with about 85% efficiency, for a total system efficiency of 68%. On the other hand if the hydrogen is used directly on board the vehicle at least 50% of the hydrogen is wasted as heat without the opportunity for waste heat recovery.
Economic competitiveness and flexibility
The most attractive attribute of the vision is the flexibility in deployment. The deployment scenario makes use of wind, solar, hydro, biomass, and tidal renewable generation, as well as nuclear, coal generation and combine heat and power. Some technologies will be more cost competitive then others. The vision can allow for various amount of each type of energy resources. For example, on the east coast, solar technologies may no be cost uncompetitive due to low solar irradiance, but the east coast has large hydro, coal and biomass resources that can be used. In the west solar is more abundant then biomass, hence more solar can be used. The vision allows for flexibility in the deployment of energy resources to meet economic, environmental and national security risks.