Carbon Dioxide Emissions from the Generation of Electricity

 Only 9% of the electricity consumed in Rhode Island in 1990 was generated in-state, rising to more than self-sufficiency (101%) in 1996, after Ocean State Power and the repowered Manchester Street Station came online.  Although the Rhode Island emissions inventory primary focuses on greenhouse gas emissions directly produced in-state because of Workbook requirements, we also present an estimate of the emissions resulting from the electricity that was imported.  Obviously, these data will be essential for estimating the impacts of demand-side management of electricity.

 In the years covered by this inventory, three major electric utilities supplied over 99% of the end users of Rhode Island: Narragansett Electric (part of the New England Electric System), Blackstone Valley Electric and Newport Electric.  The electricity they provide is supplied to them through the New England Power Pool grid.  The individual utilities purchase their electricity from a number of different power plants through the grid, based on demand and least-cost generation.  The name of the power plant and the amount of electricity purchased from the grid  is reported to the Rhode Island Public Utilities Commission in monthly Fuel Adjustment Clause reports.  The fuel these plants consumed is reported annually by the New England Power Pool in their Capacity Energy Loads and Transmission reports.  Each company also reports the amount of electricity sold in the state, broken out by sector.  We obtained these data from the RIPUC directly.  The amount and origination of electricity for each utility for the years 1990 through 1996 are presented in the Appendix - electricity generation .

 The carbon efficiency of generation (the amount of carbon emitted per unit of electricity generated) came from two sources:  E-GRID97 (http://www.epa.gov/acidrain/egrid/) and Richard Kennelly of the Conservation Law Foundation.  Conversion factors for some generating units listed by the RIPUC appeared in neither dataset and for these the average efficiency for fossil fuel units was used.  The calculations used to estimate the carbon emissions are shown in the electricity generation appendix.  Note that the efficiencies of generating units using more than one fuel will vary with the fuel mix, but for these calculations we had available only annual average efficiencies.

 The electricity consumption data for 1990 – 1996 period are given in the Electricity Consumption table, with amounts generated in-state and amounts imported shown separately.  

 Electricity Consumption in Rhode Island, in MWH  

The Carbon Emissions table lists the amount of carbon emissions (in MCTE) resulting from electricity generation in RI, primarily from new natural gas-fired facilities..  I  

Carbon Emissions from Electricity Produced  in RI (MTCE)  

The carbon emitted from generation of electricity drawn from the grid has been estimated from the carbon efficiency of the plants contributing to the grid and the Rhode Island consumption, which is reported annually  to the RI PUC.  The average carbon efficiency of generation over this six year period was higher for all electricity purchased from the grid by the three RI companies (0.18 MCTE/MWH) than for the electricity generated in RI (0.21 MCTE/MWH) presumably because the grid supply includes generation from nuclear plants and from hydro. 

Carbon Emissions from Electricity Consumed in RI (MTCE)