Sunday, August 3, 2014

Capacity Factors

In electric power generation a very important parameter affecting the quantity of power delivered and ultimately dispatched to users is the capacity factor of the generating system.

Capacity factor is defined as the total kwh (kilowatt hours) delivered in a period of time divided by the maximum possible kwh that theoretically could have been delivered in the same period of time.   The period of time is typically a year.

Certain power generation stations are peaking units and only run for short periods of time when the grid is short of power.  These power stations are typically fueled with natural gas and are a simple cycle combustion turbine.  Some thermal power stations also run to provide ancillary support or spinning reserve to the grid and are not dispatching power to customers but simply keeping the voltage and frequency within specification.

Renewable energy power stations such as solar cells or wind have to rely on gas powered stations to provide voltage and frequency support and their capacity factor is also lower due to the intermittency of the renewable energy source (wind or sunshine).

The EIA does report on capacity factors for various sources of energy that are either renewable or fossil fuel based.  Nuclear and geothermal have the highest capacity factors and wind, solar, hydro and simple cycle peaking units have the lowest capacity factor.  This makes sense one cannot run a nuclear power station intermittently. 

Bloom Energy had claimed in Delaware they would have a capacity factor of 96% but actually only achieved 84% over a year reporting period.  Additionally this level was achieved as DELMARVA the utility gives the Bloom Boxes first priority in dispatching power to grid.  GE and other wind turbine manufacturers claim capacity factors of over 50% for their latest product offering yet wind energy has not increased its capacity factor over the past three years.    The peaking unit combustion turbines have a very low capacity factor of only approximately 5%.

From the above one can see that the grid is a complex system and much surplus capacity needs to be in place to keep power quality and reliability acceptable.   Even Apple Computer overstates their capacity factor for their large 40 MW PV power station in Maiden NC.  Apple unfortunately sited this large privately owned power generation station in one of the rainiest spots in the country.  The rains are also constant month by month and season by season over the year.  We are fortunate in California that we have winter rain and winter is when the sun is the lowest and PV power is hardly generated.  Apple should have sited this power station in Arizona or California and not North Carolina.

A friend installed 1.6 MW of PV cells on the roof of a warehouse in the Bronx NY and the capacity factor of this system has been far lower than was expected.  Sadly the capacity factor is around 12%.   My guess is there are a lot of sea gulls and pigeons who take aim at the roof.  Also the amount of dirt and soot on the PV modules in the Bronx will diminish the actual power than can be generated from the roof mounted station.   Additionally the contractor may have installed inferior panels, inverters, controllers, and transformers and all of these contribute to the diminishment of the quantity of kwh in AC form that are actually dispatched to the grid.  Shading of one panel by adjacent panels or shading by surrounding buildings and vegetation also diminishes the amount of power actually dispatched.

Developers of all power projects should pay careful attention to the real capacity factor that can be achieved in projects and all the companies who sell power generation systems tend to provide estimates of capacity factors under ideal conditions that actually never result.   Bloom promised 96% capacity factor and they also promised green energy.  They deliver neither but get paid a lot of money for their electrons not because of their electrical connection but their political connection.   Interesting Senator Feinstein who has assisted me with the US FTC investigation of the greenwashing by Bloom was one of the dignitaries who videod in to the formal launching of Bloom in February 2010.

I guess four years later after the real data on Bloom’ s performance is now known those like Ms. Feinstein with a brain and eyes can clearly see that Bloom hyped their performance and can say they were duped.  Sadly this company continues to hype their performance and their capacity to greenwash is 100%.  Perhaps some smart lawyers will be able to go after GE for hyping their capacity factor of over 50% on wind turbines if in fact it turns out that in the real world this is not so.   Remember the EPA has determined that carbon dioxide is harmful to the health and welfare of Americans.   If the Bloom Boxes and the GE Wind Turbines do not deliver as promised more power from inefficient coal and simple cycle gas fired stations is needed.  The clever lawyers will claim that like the tobacco companies these green hypers have adversely affected the health and well-being of people.   One does not have to smoke to inhale the excess CO2 so even Bill Clinton may join the class of affected citizens.   Al Gore will be a defendant as he is closely involved with Bloom and his fund once held a lot of stock in GE.

The latest holdings of Al Jazeera Gore's fund are in the link below