Now that we know the exact permitted potential use of the existing and prospective boilers – at both West Campus Steam Plant and East Campus Steam Plant – we’re trying to do some maximum fuel consumption and maximum potential emissions estimates – along with some 20-year natural gas cost projections in a stable price scenario (Penn State’s working assumption as of April 2013), medium-increase price scenario and high-increase price scenario. (More info about supply and demand factors and trends at US-EIA Natural Gas page.)
Some of our rough calculations so far:
The limit in #10 of the Plan Approval uses 6,500 hours/year of operation for the two new WCSP boilers at 198 mmBtu/hr. Some calculations in Appendix D used 6100 hours, leaving 400 hours for fuel oil. But assuming the #10 permit limit is it, here are the maximum permitted natural gas consumption rates at WCSP (scf = standard cubic feet):
- New Boiler #1 – 198,000 scf/hr * 6500 hrs/yr = 1,287 million scf/yr
- New Boiler #2 – 198,000 scf/hr * 6500 hrs/yr = 1,287 million scf/yr
- Modified Boiler #6 – 49,000 scf/hr * 2000 hrs/yr = 98 million scf/yr
- Modified Boiler #8 – 49,000 scf/hr * 2000 hrs/yr = 98 million scf/yr
- WCSP Total – 2,770 million scf/yr
- Boiler #1 127,450 scf/hr * 2550 hrs/yr = 325 million scf/yr
- Boiler #2 127,450 scf/hr * 2550 hrs/yr = 325 million scf/yr
- Combustion Turbine – 673 million scf/yr if no oil is burned
- Duct Burner on HRSG – 294 million scf/yr
- ECSP Total – 1,617 million scf/yr
Overall total potential annual natural gas consumption for just the two power plants – 4,387 million scf/yr
For the next few years, Penn State is unlikely to burn the full permitted volume of gas, because steam heat demand is seasonal rather than year-round. However, if the proposed CT/HRSG unit is installed at the WCSP, fuel consumption will increase, because electricity is a year-round demand.
Carbon dioxide emissions in metric tons (2,204 pounds) are calculated by mulitplying the mmBtu of the delivered gas times an emissions factor of 53.06 kg CO2/mmBtu.
Burning that maximum permitted amount of gas will release roughly 235,000 metric tons of greenhouse gas equivalents (not counting methane release between the wellheads and the power plants).
For comparison, the 2012 actual emissions – as reported to EPA – from all greenhouse gas sources at Penn State – including both steam plants, building generators, smaller boilers and other emissions sources (listed in the general operating permit pp. 4-6) – was 168,048 metric tons.
Part of Penn State’s reasoning for heading down the natural-gas dependent path, especially the CT/HRSG units (and this is speculation because they haven’t yet publicly released the Energy System Master Plan that would illuminate their long-term energy strategies) is a desire to decrease campus dependency on the regional electric grid, and thereby decrease demand on the coal-fired power plants in the southwest part of the State.
In calculating greenhouse gas emissions for EPA reporting purposes and for DEP permitting purposes, Penn State used a default of 1000 Btu/cf for natural gas. However, the heat content of natural gas can be as high as 1,200 to 1,300 Btu/cf, depending on the chemical composition of the source gas. Higher overall mmBtu consumption means higher emissions, potentially more than 20% higher.
According to several reports, Marcellus Shale gas has a higher Btu content, and Columbia Gas charges for gas delivery based on a Btu content adjustment:
- 10.4.10 – Columbia Gas of Pa. Seeks to Apply BTU Content Adjustment to Monthly Billing MCFs
- 2.2.12 – Columbia Gas customers may pay more
- High BTU Fuel Gas from the Marcellus Shale and how it Affects Emissions and Peak Firing Pressures
Columbia Gas updates the adjustment factors monthly, based on readings at the “Pipeline Scheduling Point” nearest the end-use customer’s location.
If any readers are Columbia Gas customers who live in or near downtown (where the West Campus Steam Plant is located) and you have a handy copy of a recent bill showing the Btu adjustment factor, please let me know.
Differing Btu/cf ratios affect calculation of greenhouse gas emissions and all other emissions in the permits for natural gas combustion.