Starting in 2009 Ohio law has mandated that investor-owned electric utilities meet specific annual goals for renewable electricity ( Ref. a). The PUCO web site reports the in-state renewable energy requirements for all years up to 2025 (b).This note provides information on how well we are meeting these requirements.
The Appendices provide background information. Appendix A is a primer on electricity terminology, while Appendix B provides the relations among the terms that I have used. Appendix C discusses the relative costs of various energy sources.
The non-solar goal for 2025 is 8.67 million MWh, requiring 2000 to 3300 MW capacity. Current thinking is that the bulk of Ohio's renewable electricity will be provided by wind and biomass. By the end of 2011 Ohio will have 400 MW of wind power (c). There also will be some electricity from biomass, although the amount is very uncertain. I have estimated two limits for biomass:
37 MW – only the power available using landfill gas (d)
251 MW – the total biomass renewable power approved by PUCO (e)
Using the mathematical relations from Table A-2 Ohio's current capacity can provide between 1.2 and 2.4 million MWh annually. Even if the lower limit is correct, Ohio already has about enough non-solar capacity to satisfy its 2013 goals.
The solar goal for 2025 is 361 thousand Mwh, requiring about 300 MW capacity
Ohio now has 28 MW of solar energy (f), which can produce about 34,300 Mwh of electricity annually. This amount is only 88 percent of the 2012 goal. However, there is reason to believe that this shortfall has been corrected (g).
References
b. http://www.puco.gov/ “Ohio Alternative Energy Portfolio Standard – Certified Renewable Energy Facilities (as of 11/01/11)
c. E. Thumma: Testimony before the Joint Public Utilities Committees of the Ohio
General Assembly (11/02/11)
e. www.puco.gov “OHIO’S ALTERNATIVE ENERGY PORTFOLIO STANDARD - CERTIFIED RENEWABLE ENERGY FACILITIES”
f. Colin Marchie: Testimony before the Joint Public Utilities Committees of the Ohio
General Assembly (11/02/11)
g. First energy Press Release, 07 Nov. 2011
APPENDIX A - BACKGROUND
A-1. This is a section about basic electrical units for newbies. You are probably aware of two ways of measuring electricity: your monthly bill reports how much you have used in kilowatt-hours (kWh) and the number of watts (W) in a light bulb tells you how brightly it will shine.
When we write about the electricity that the whole state produces, we need to use bigger units. Power plants (whether coal, nuclear, or wind turbine) are rated in Megawatts (MW, where 1 MW = 1000 kilowatts [kW] and 1,000,000 watts [W]). It is important to understand that watts measure the rate of producing or consuming energy – 1 kilowatt means that a power plant can produce 1 kilowatt-hour of electricity every hour.
To find the amount of electricity produced by a generator or used by a piece of equipment, its watts (or kilowatts) need to be multiplied by the time that it is working: a 100 watt light bulb burning for four hours requires 400 watt-hours (or 0.4 kWh) of electricity.
While Watts measure rates of production or consumption, the units containing hours, such as kWh, measure the total amount produced or consumed. The same relations apply : 1,000 Wh = 1 kWh, 1,000 kWh = 1 MWh.
A-2. The capacity factor is an additional complication. It takes into account variability in operating time and power. Formally, the capacity factor is the ratio of how much electricity is produced to how much would be produced if a unit was running at full power all of the time. For example, a solar array could never run more than 50 percent of the time, because the sun only shines half of the time during the course of a year (actual capacity factors for solar arrays are much smaller because of cloud cover). Table A-1 reports the values of capacity factor that I have been using. Different technologies have different capacity factors and capacity factor may vary for different installations (a location with more frequent high winds will have a higher capacity factor than one less-well sited).
Table A-1. Typical values of capacity factor. (all values are from the U.S. Energy Information Administration [EIA] “Average Capacity Factor by Energy Source”, except as otherwise noted)
Nuclear = 0.92
Landfill Gas = 0.85, based on various sources
Coal = 0.74
Biomass, purpose-built plant = 0.7, based on Glatfelter PUCO data
Biomass, co-fired in coal plant = 0.5, based on PUCO Duke calculation
Hydro = 0.36
Wind = 0.30, based on Blue Creek and Timber Road web sites.
Solar PV = 0.14, Value used by DPL in PUCO submission
Ohio renewable average, according to EIA for 2007 (latest available) = 0.45
Replacing one type of generator with another results in a different amount of electricity (MWh) for the same power (MW). To get the same amount of electricity from each source, multiply the power by the ratio of capacity factors. For example for each MW of coal replaced, the wind requirement is the ratio of the coal capacity factor to the wind capacity factor = 0.74/0.30 or about 2.5. To replace a 500 MW coal Pant requires about 1250 MW of wind power.
A-3. This section concerns estimating annual electricity production form a power source. I used the mathematical relations in Appendix B for these estimates. Two values are reported: the output per megawatt is in parentheses ( ) and the number of households that can be powered by one megawatt. According to EIA, the typical Ohio home uses about 11,000 kWh annually.
Table A-2 – Annual Electricity Production from a Power Source per Megawatt of Capacity
Power Source
|
MWh per MW
|
Houses per
MW
|
Nuclear
|
8060
|
735
|
Landfill Gas
|
7450
|
680
|
Coal
|
6480
|
590
|
Biomass*
|
5260
|
480
|
Hydro
|
3150
|
290
|
Wind
|
2630
|
240
|
Solar PV
|
1225
|
110
|
* Average values based on the two estimates in Table A-1 have been used.
As an example, a 2 MW wind turbine can supply enough electricity for almost 500 households.
Appendix B – Mathematical Relations
B-1: Calculation of Goals
The basic relation between capacity and energy is:
E = PCt = 8760PC ...(1)
where:
E = electrical output in MWh
P = source capacity in MW
C = capacity factor
t = time = 8760 hr/yr
To find the annual capacity required to meet Ohio's goals, we define two new terms:
E* = annual renewable consumption to be generated in Ohio in mWh
P* = Required capacity, depends on power source in MW
Rearranging Eq. (1)
P* = E*/Ct = E*/8760C ... (2)
Non-Solar
Because the non-solar goal will be met by using several technologies (c), the overall capacity factor is unknown. Taking limits of C of 0.3 and 0.5:
R* = 8.67 MWH
From Eq. (2): P* = 2000 to 3300 MW.
Solar Set-aside
R* = 361 thousand MWh
From Eq. (2): P* = 300 MW
B-2 Calculation of the number of Households Served
If H = The number of households that can be powered per MW of electricity varies with energy source:
PCt = eH ...(3)
Rearranging:
H/P = Ct/e = 800C ... (4)
where e = average household requirement = 11,000 kWh/yr. (EIA estimate for Ohio)