Reducing Emissions Quickly – Setting Priorities

In 1992, the first COP Conference in Brazil recognized the need to reduce emissions. At the time, 87% of global energy needs were met with fossil fuel. It was agreed that this needed to change dramatically. More recently, it has been suggested that to stay within the target temperature increase, a net-zero target needs to be achieved by 2050. We are now slightly more than half-way through the time between 1992 and 2050, and the reliance on fossil fuels has declined to 83%, but, in fact, more fossil fuel is now used annually than in 1992. There is a common view, that the target is to displace all fossil fuel energy sources with renewable sources. Between 2010 and 2020, the US renewable share (solar and wind), grew from 1.06% to 4.6% of total energy. Renewables will obviously be an important asset in future, but the transition appears to be too slow to meet the net zero target in 2050.

Recent climate events have brought a strong focus on this issue. Net-zero emission is not a final solution but is simply the point at which the weather impacts stop getting worse. We may see increases in weather events until net-zero is achieved, declining only as levels of atmospheric carbon decline very slowly after that time. Without other means, the decline could take more than 1,000 years.  

To minimize the total atmospheric carbon when net zero is achieved, immediate changes are needed to reduce emissions. This may be achieved through conservation or by increasing efficiency of energy production, delivery and use. The current efficiency of the energy systems, from primary sources to the delivery of useful work is less than 35%1. Action is important in both the transition to clean energy and in the delivery and use of energy. As these activities are independent, simultaneous improvements may be implemented in both areas.

The electric grid currently delivers about 20% of total energy needs. Electrification of all fossil fuel demands would require a dramatic increase in electric power and energy capacity, and this has been seen to be unfeasible or near impossible in the short term. Efficiency improvements and/or conservation activities can potentially provide immediate emission reductions.

As the electric grid has limited near term capacity for electrification, the ratio of emissions to energy required is a useful tool to be used to establish priorities. A higher ratio would indicate a greater reduction in emissions for the electrical energy required. This would maximize emission reduction results in the near term.  

Two examples receiving a lot of attention are the conversion of natural gas heating systems to electric heat pumps, and the conversion of gasoline powered (ICE) vehicles to battery electric vehicles (BEV). Applying a ratio approach to these two examples enables us to see which would have more immediate and greater benefits in reducing emissions without over taxing the electric systems.

In comparing these two conversion strategies, the following assumptions are made:

  • Natural gas is assumed to create 55.82 kg/GJ
  • 1 L of Gasoline burned will create 2.3 kg of emissions and deliver 0.0342 GJ of energy
  • Gas Furnace – Heat pump conversion
    • Electricity is assumed to be clean, producing 0 kg/GJ
    • Heat pump COP (Coefficient of performance) will be 2-4
    • Gas furnace efficiency will be 95%
  • ICE Vehicle to BEV Conversion
    • Toyota RAV 4 (Best mileage in small SUV Class) EPA rating for combined city/highway use 7.85 L/100 kM
    • Tesla Model Y (Long range AWD) EPA rating for combined city/highway use of 27 kWh/100 – 1.88 L/100 kM

A heat pump will deliver 2 – 4 times the amount of heat energy than is consumed by the system. We will consider 2 operating states, one at a COP = 2.0 and one at COP = 4.0. At COP of 2, the ratio is 124, while at COP = 4, the ratio is 248. By comparison, the ratio for a transition from a RAV 4 to a Tesla Model Y is 692. Considering that over 70% of new vehicle sales are for either light trucks or SUVs, and the RAV 4 was identified as one of the most efficient of the SUV vehicles, the transition that achieves maximum emission reductions/electrical energy used is the conversion of electric vehicles to BEV technology. Furthermore, if the average COP over a year for the heat pump is significantly less than 4 (which is likely) the resulting difference is significantly more dramatic. The BEV may give up to almost 4x the emission reduction per kWh of electricity consumed.

BEV technology may have an additional added benefit, and that is a potential to allow the electric utility to manage the timing of charging, either using a rate structure or a real-time control facility to manage the use of home chargers. In using this concept, the utility may be able to increase the capacity use of their delivery system at the same time as managing and reducing system loss.

A careful plan is needed to achieve maximum emission reduction using the available electricity supply. Other alternative conversions may need to be considered but given the common recommendations being the electrification of home heating and personal vehicles, the BEV technology should be considered as a priority, even while acknowledging that both are currently major sources of emissions to the extent that they rely on fossil fuels.

There may be other benefits hidden in this transition. Homeowners may find solar installations may deliver added benefits with the inclusion of battery storage. With this addition, the system can provide additional home backup capacity and time of use cost mitigation. By participating in partnerships with utilities, owners can further benefit by collecting revenue for demand management, frequency regulation and reserves for the utility. The needs for these services will have growing value as the penetration of intermittent generation increases. Generac may improve value with a dual focus, on integrating renewables, and on maximizing the benefits for both homeowners and utilities.


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