This article is focused on operational energy and how it should be added, classified and reported to meet EN15978 standard. This is particularly relevant for on-site energy generation (i.e. Solar PV).
How to correctly add on-site energy generation to an eTool model?
How to correctly categorise energy consumption entries between B6 and B6+?
In eTool, building energy use is divided into building related energy (module B6: HVAC, Lighting, Water Heating, Lifts, BMS) and non-building related energy (module B6+: plug-in appliances) and the user can select the appropriate reporting module when adding operational energy item. On-site generated solar electricity is divided into solar electricity used on site (module B6) and solar electricity exported to the grid (module D1).
The video below demonstrates the process for a detached residence in WA Australia.
- The Operational Energy page shows annual electricity use and generation for the whole residence. Although the design is net zero operational energy (MJ/year) it still has a small carbon impact (kgCO2e/year). The GWP coefficient for the export grid is lower due to reduced distribution losses.
- The EN15978 table shows the impacts distributed in different modules. Note the other Life Cycle modules were “turned off” (MNA) just to simplify the example.
- When editing operational energy you can see how the electricity use and generation is included in the LCA models with correct allocation of grid and reporting module. This is important when producing EN15978 compliant LCA studies.
With specific regards to on-site energy generation for solar PV systems, some assumptions/references will need to be made for the proportion of energy that is directly utilised on-site and energy that is exported. If you’d like to refine this energy use allocation, please refer to an energy consultant for advice on what the ratio should typically be for your particular project. The default eTool PV template from the library automatically assumes a 50/50 ratio of on-site utilisation versus energy exported. The ‘X’s below represents the energy generated which varies depending on the size of your PV system.
In the example below, we’ve assumed a proportion of 80/20 (on-site utlisation/exported) for the PV energy produced. We would say that this 80/20 split is fairly typical for standard office buildings as they’re usually occupied during the day time on weekdays therefore most of the energy production will be utilised on-site. However, this would also depend on the solar PV size as a smaller system for a large building will most likely have a lower export rate.
Note that the *2 in the formula is to account for the total energy generation before the % split. Also note the Grid/Network and Reporting Modules specified for the two different energy sources – grid import + B6 for onsite use and grid export + D1 for energy exported.
Related posts: Over 10% increase in Ozone Depletion (ODP) or Abiotic Resource Depletion Potential (ADP) causing potential loss of Green Star LCA Credits, How to Reduce ADP/ODP Increase in Large PV Systems