Process and Device Energy

Process and Device Efficiency – ENERGY 2100 simulates both the process energy efficiency (economic output produced per unit of service energy) and the device energy efficiency (service energy per unit of fuel inputs) to compute energy demands.  This is important for a number of reasons:


    1. The lifetime of a factory, commercial buildings or residential home is longer than the lifetime of a device (motor, furnace, refrigerator) so the vintaging of the process capital stock is different from the device capital stock.
    2. The process efficiency may be decreasing while the device efficiency is increasing; for example, there may be less economic output per lumens in a grocery store (the grocery store is brighter) while the light fixtures are producing more lumens per unit of electricity
    3. Policies will generally be directed at either process or device efficiency, so the model needs to be able distinguish between a process and a device policy to accurately model the policy.


Two policies (one for process and one for device efficiency) will interact, so to calculate the interaction both process and device must be modeled.


Process energy efficiency: ENERGY 2020 distinguishes between process and device energy. Process energy refers to general forms of energy required by consumers, such as the amount of heating, cooling, lighting, or industrial processes energy required each year. Process energy represents the general type of energy requirement which is in contrast to device energy which represents the specific devices used to meet the total process energy requirements, such as furnaces, air conditioners, or light bulbs. The amount of process energy required by consumers is impacted by the efficiency of the systems requiring energy. For example, the process energy efficiency of residential heating system represents how much heating is required per unit of floor space. One of the factors influencing the process energy efficiency would be the efficiency of the building shell. Increasing insulation levels would decrease the amount of heating energy required per unit of floor space.

A marginal process energy efficiency is calculated in the model (during model initialization) using an efficiency-price response curve. Policies can be introduced to increase the business-as-usual level of process energy efficiency. Implementing a building code (which establishes a minimum building shell efficiency) is an example of a policy that would impact process efficiency. Other examples of policies that increase process efficiency include promotions encouraging consumers to reduce their vehicle distance traveled each year or obtaining commitments from industrial customers to use energy more efficiently in their industrial processes. 

Device energy efficiency:  In contrast to process energy, device energy represents the amount of energy consumed by devices, machines, or end uses, such as furnaces, light bulbs, and cars. The device energy efficiency is measured as the ratio of energy output per energy input for a specified device. For example, electric space heating energy efficiency is measured as the amount of heat output per energy used to create the heat. Device energy efficiency is calculated in the business-as-usual case based on principles of consumer choice theory combined with an efficiency-fuel price curve.


Policies can be introduced to modify the device energy efficiency levels of the business-as-usual case. Examples of policies that impact device energy efficiency include appliance/equipment standards that establish minimum device efficiencies for residential appliances, commercial and industrial equipment, and transportation vehicles. Other types of policies, such as energy efficiency programs, directly increase energy efficiency rather than setting a minimum standard. These energy efficiency programs encourage behaviors that increase energy efficiency as well as encourage purchases of energy efficient processes and devices.