Thermal Solar in the California Desert
- Oct 29, 2010 5:33 am GMT
- 320 views
A recent article on the New York Times Greenwire website describes the Blythe Solar Power Project, BSPP. See below website.
BSPP is a 968 MW thermal solar plant on 9,400 acres in the California Mojave desert leased from the Bureau of Land Management, BLM; of this land 7,025 acres will be taken up by the BSPP.
The plant consists of (4) 242 MW units. It has air-cooled condensers to minimize water use. The expected total energy is 2,200 GWh/yr which will be purchased by Southern California Edison, SCE, under a power purchase agreement, PPA. SCE is connected to the California grid that is managed by the California Independent System Operator, CAISO.
The plant will built in 2 stages and will take at least 6 years to complete. The capital cost is estimated at $6 billion, or $6,200/kW. A more complete description can be found in the project application documents. See below website.
For the first phase, the Department of Energy will provide a $2.1 billion loan guarantee as well as a $0.9 billion grant (30% of the $3 billion capital cost) for Units 1 and 2. There will be about 1,000 jobs during the construction phase and about 80 permanent jobs during the O&M phase.
The BSPP will utilize solar parabolic troughs to generate electricity. Arrays of parabolic mirrors collect heat energy from the sun and focus the radiation on a receiver tube located at the focal point of the parabola.
A synthetic hydrocarbon is used as a heat transfer fluid (HTF) that is heated to high temperatures (750 degrees F) as it is piped through the receiver tubes. The HTF is then piped through a series of heat exchangers where it releases stored heat to generate high-pressure steam. The steam is fed to a traditional steam turbine generator.
The annual production will be 968 MW x 8,760 hrs/y x capacity factor 0.26 = 2,200 GWh. The production varies daily and seasonally with the strength of the sun and is available ONLY DURING THE SUNSHINE HOURS OF THE DAY. The plant is started in the morning and shut down in the evening, i.e., about 65-70 percent of the year the solar energy is near-zero or zero.
The NYTimes article states this energy is enough for roughly 800,000 households. As a California household uses about 6,000 kWh/yr, about 4,800 GWh/yr would be required by these households, but the plant produces only 2,200 GWh/yr.
The NYTimes statement is grossly inaccurate, unless the writer meant that the power is enough only during the sunshine hours of the day. Other energy sources, such as pumped storage hydro, nuclear, wind, stored biogas (CO2 emitting) and fossil (CO2 emitting) will be needed to supply the remaining 2,600 GWh/yr.
INTEGRATING VARIABLE ENERGY SOURCES INTO THE GRID
As variable/intermittent energy, such as from thermal solar, PV solar and wind, becomes a greater percentage of the energy mix on the grid, a greater capacity of standby, spinning and balancing plants are needed to ramp down when variable energy surges and ramp up when it ebbs to maintain the grid voltage and frequency at required values and to prevent brownouts and blackouts.
The spinning plants usually are fossil power plants that are running without sending power to the grid, but they can be called on to quickly increase their outputs as required. The balancing plants usually are quick-ramping, open and closed cycle gas turbines.
Plants can be quickly started and stopped, but it causes increased wear and tear and is inefficient. Plants cannot be operated below a certain output, because combustion and air pollution control systems become unstable. Plants operating at very low loads, or in spinning mode, cannot be shut down, because their energy will likely be needed to maintain balance on the grid, if solar energy ebbs due to variable cloud cover.
Note: Gas turbines cannot be efficiently operated below about 50% of rated capacity, which limits their part-load-ramping mode.
Note: About 65-70% of the hours of a year there is near-zero solar energy. Solar energy is minimal in the morning, maximal at noon about 3-5 hours before the daily peak demand, minimal in the afternoon and on cloudy, snowy days, and zero at night. During variable cloudy weather, solar energy varies even more, percentage wise, than wind energy, as often happens in Southern Germany.
In Southern Germany, with about 1,000,000 PV system installations, on clear-sky-sunny days, the PV solar energy surges to at least 15,000 MW at around noon, some of which is used in Southern Germany and the rest is exported to France at grid prices of about 5.5 euro c/kWh, after having been subsidized at feed-in tariffs of up to 60 euro c/kWh; feed-in tariffs have been decreasing in recent years. On variable-cloudy days, the solar energy may vary at much as 50% within short time periods.
Note: About 10-15% of the hours of a year there is near-zero wind energy, because wind speeds are too low (less than 7.5 mph) to turn the rotors or too high for safety. During those hours, wind turbines draw energy, a.k.a. parasitic energy, from the grid which can be 10-20% of turbine capacity on cold winter nights. Wind energy is minimal during summer, moderate during spring and fall, and maximal during winter; at nearly all times it is maximal at night when demand is low, which often calls for curtailment of wind energy by feathering the blades or stopping the rotors.
Because there will be many hours during the year when wind and solar energy are near-zero, nearly ALL of the existing capacity of conventional plants needs to kept in good operating condition, staffed 24/7/365, fueled, i.e., ready to provide energy when wind and solar energy is insufficient.
These conventional plants will have reduced outputs with wind energy on the grid which adversely affects their economics; in Germany, owners of conventional plants are rebelling and owners of wind turbine facilities are rebelling because of wind energy curtailments, and demand to be paid for lost production.
Example: Owners are paid $18 to $50 million per year for not producing energy within the Bonneville Power Authority service area during curtailment periods.
Another approach, used by nations with high percentages of wind energy AND access to hydro plants, such as Denmark, Spain and Portugal, is to use pumped-storage hydro plants and natural gas-fired gas turbine plants to “smooth” wind energy.
A third approach is detailed below under A GERMAN RENEWABLE POWER DEMONSTRATION.
ENVIRONMENTAL IMPACTS OF THE PROJECT
The land will be leveled by bulldozers to accommodate the arrays. Even though it is desert, no fauna and flora lives there?
The 11 square miles of surface area of the 968 MW BSPP plant may create a small heat island in the desert, hotter than an equivalent desert surface that is now partially covered with vegetation.
About 48,000 MW of CSP plants, similar to the BSPP plant, are in the planning stages. These plants will require about 11 x 48,000/968 = 550 square miles which may affect the local climate. A new, hotter eco-balance may be created in that area. It runs counter to having white roofs on buildings in urban areas to reduce heat island effects.
LEGISLATIVE MANDATES AND TAX CREDITS
The forces that drive this project is California’s renewables mandate for utilities and the 30% federal tax credit; about $2 billion in this case. If a developer has no taxable profits and thus cannot use the tax credit, he can opt to get a check for $2 billion from the federal government. i.e., that is from all of us.
THERMAL SOLAR ENERGY COMPARED WITH NUCLEAR ENERGY
A standard 1,000 MW nuclear plant for about the same cost as the above thermal solar plant would produce = 1,000,000 kW x 8,760 hrs/yr x CF 0.90 = 7,884,000,000 kWh/yr, 3.6 times the power of thermal solar plant.
This power is steady and 24/7/365, i.e., it is available DURING ALL HOURS OF THE DAY, CO2-free, and will serve ALL the power needs of 1,314,000 California households for a year.
A US NRC list of US nuclear plants shows that most of the plants have plant sites of about 500-1,000 acres, 7% – 14% of the land area for a 1,000 MW thermal solar plant. See below website.
Given the above, it is to be expected that the smart and knowledgeable power industry experts in at least 30 major nations, such as the US, the UK, France, Sweden, China , India, etc., have convinced their governments to continue to opt for nuclear power as a major component of their future power mix. To do otherwise leads to expensive renewable energy follies, as in Germany.
A GERMAN RENEWABLE POWER DEMONSTRATION
Several German power industry experts created, for demonstration purposes, a “renewables utility company” that uses several field-mounted, sun-tracking PV solar plants in southern Germany, several wind farms in northern Germany, several biogas-fueled combined cycle gas turbine, CCGT, plants with biogas storage tanks, and several pumped storage hydro plants, all controlled from one command/control center to maintain a load following output to the grid.
The experts maintain that as it was shown to be technically feasible to maintain a load following output to the grid for a small combination of renewable power plants, it will be feasible for increasingly larger combinations as well.
THE US CONDITION
Germany’s national electric grid is owned by four major power companies, each with their own service area. It is much smaller and more compact than the US national grid. It is designed to strict standards and has the lowest outage rate in Europe. Germany’s national energy policy, which has been in existance for decades, requires it be redesigned to accommodate increasing renewable power percentages to its power mix.
The US faces major obstacles to increasing the renewables percentage of its power mix, such as:
– fragmented, outdated grids poorly suited to renewable energy.
– a grid design influenced by an historic reliance on plentiful and cheap supplies of fossil fuels, especially coal.
– powerful oil and coal industries often opposed to incentives for renewables development.
– energy policy heavily influenced by individual states.
For the “renewables utility company” approach to work in the US, its grid, with about 1,000,000 MW of power plants connected to it, will need to be rebuilt so the grid and the power plants can all be controlled from only a few command/control centers. The capital cost to implement these changes will be in the order of $200-$300 billion during the next 30 years. Going “variable and renewable” has its costs.
The US has about 100,000 MW of nuclear plants in operation. They produce about 20% of US electricity. As an alternative the $200-$300 billion could be used to replace 33,000-50,000 MW of the older US nuclear plants; no significant changes to the grid would be required.