Chapter 6: Evaluating US Energy Solutions
by Brian Gitt
The Better Energy Strategy aims at evaluating each energy source that’s available in a given place to determine which ones offer the best balance of human and environmental costs and benefits. What’s best for one place isn’t necessarily best for another. Local conditions—geological, meteorological, political, and economic—affect what works best.
I plan to focus on energy solutions for the US. The US is lucky: it has many natural resources in abundance, a stable political infrastructure, and an advanced level of economic and technological development. As a result, it has many feasible energy options. Among them, I’m going to focus on the energy sources used to generate electricity. That means I’m not going to evaluate oil and biofuels, since the US doesn’t use either of those to generate electricity. I’m also not going to discuss coal and hydro power because neither is politically feasible in the US. Environmental lobbyists strongly oppose the construction of new hydroelectric dams, and the EPA is stepping up efforts to close existing coal plants in the US.
I’m going to focus instead on six energy sources: solar, onshore wind, offshore wind, large nuclear, small nuclear, and natural gas.
When we evaluate these energy sources, two come out on top: nuclear and natural gas. They’re not perfect. No energy solution is perfect. All have their tradeoffs, nuclear and natural gas included. But in the US, which is technologically and economically advanced and blessed with abundant natural gas, the shortcomings of nuclear and natural gas are more manageable than the alternatives, and their advantages can’t be beat.
The following table ranks these six energy sources in each of the human and environmental categories I’ve described. The top-ranking energy source in a given category receives a score of 1, and the other energy sources in that category receive scores between 2 and 6. In the case of a tie, two energy sources receive the same score. Because the best scoring energy sources receive lower numbers, the lowest total numbers reflect the best overall energy sources for the US.
I’ve not assigned weights to the different categories. The reason is that those categories might be weighted differently in different contexts. The US is a large country, and different regions have different conditions that might affect which factors matter most there. Trying to evaluate energy solutions for different US regions would take us too far afield for our purpose here, which is simply to illustrate how to evaluate energy sources using the factors I’ve outlined.
The remainder of this chapter describes these energy sources. The following chapters explain why I ranked them in each category as I did.
Large nuclear
A large nuclear power plant has a capacity of more than 1,000 megawatts (MW). One MW provides enough electricity to power 600 to 1,000 homes. (The exact number of homes depends on how much energy the average household consumes, which depends on a number of factors, including climate and the number and size of household appliances.) Therefore, a 1,000 MW plant would provide enough electricity for 600,000 to 1 million homes. The most common type of nuclear power plant in the US is the pressurized water reactor (PWR). PWRs use enriched uranium as fuel and pressurized water as both a coolant and a neutron moderator. The water is heated in the reactor core by nuclear fission and is then pumped through a steam generator, where it heats a secondary loop of water to produce steam. The steam drives a turbine generator which produces electricity.
Small nuclear
I define a small nuclear power plant as one with a capacity of 600 MW or less. (Note that others sometimes define small nuclear plants as plants with capacity of less than 300 MW, and they define plants with capacities between 300MW and 1,000 MW as medium-sized plants.) The kind of small nuclear power plant I’m focusing on is a Small Modular Reactor (SMR). SMRs are modular because their components can be made in a factory and then transported to the site where they’ll be used. Large nuclear reactors, by contrast, must be built on site.
Natural gas
There are two types of natural gas power plants:
Simple cycle gas-fired combustion turbine plants: These power plants use natural gas to fuel a combustion turbine that drives a generator to produce electricity. The gas is burned in the turbine to produce a high-pressure stream of hot gasses, which then expands through the turbine blades to generate electricity. Gas-fired combustion turbine plants are often used for peaking power output where electricity demand is highest, because they can be engaged and stopped quickly and can reach full power output within minutes.
Combined cycle gas turbine plant (CCGT plants): These power plants use a two-stage process to generate electricity from natural gas. The first stage burns natural gas like a gas-fired combustion turbine does. But the second stage uses the hot gasses produced by the combustion turbine to heat water and produce steam, which then drives a steam turbine to generate additional electricity. CCGT plants are more efficient than simple cycle gas-fired combustion turbine plants because they recover the waste heat from the combustion turbine. They are, however, more expensive to build and operate. CCGT plants are often used for baseload power, where electricity demand is constant and high, instead of for peaking power.
In my analysis in the table above, I’m referencing the more efficient CCGT plant.
Solar photovoltaic (PV) power plants
Solar power plants use solar panels to convert sunlight directly into electricity. The panels are made up of many small solar cells, which are connected to form a module. The modules are then connected in series and parallel to form an array that can generate large amounts of electricity. For my analysis, I’m referencing a 150 MW ground-mounted solar plant with single-access tracking. Tracking technologies periodically realign solar panels so they follow the path of the sun as it moves across the sky. Single-axis tracking systems rotate the solar panels around a single axis, typically a horizontal or vertical axis, to optimize their orientation toward the sun.
Onshore wind
An onshore wind power plant generates electricity from wind energy using land-based wind turbines. The turbines are typically installed in areas with high wind speeds, such as on hills, ridges, or open plains. Each turbine consists of a tower, a rotor with two or three blades, a generator, and various control systems. Wind energy is harnessed by the blades, which turn a rotor. The rotor is connected to a generator which converts the rotational energy into electricity. My analysis references a 200MW wind plant with 2.82 MW wind turbine generators.
Offshore wind
An offshore wind power plant generates electricity from wind turbines that are located offshore—typically in the ocean. Offshore wind turbines are installed on fixed or floating platforms anchored to the seabed or to buoyant devices and are connected to an onshore electrical grid through a subsea cable. Offshore wind turbines use the same technology as onshore turbines, but they’re generally larger and more powerful due to the stronger and more consistent winds available at sea. My analysis uses a 400 MW plant with 10 MW wind turbine generators.
The chapters that follow explain how I arrived at my rankings in each category.