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Comparing the energy balance

One variant is only better than another once it is clear what exactly is being compared. EPOS-Plan provides the complete energy balance of a year for this purpose – not only annual totals but the time course from which coverage, residuals and surpluses are derived.

Balance boundary and reference quantities

The basis of every comparison is an unambiguous balance boundary. On the heat side stands the useful heat demand from space heating, hot water and process heat, supplemented by network and storage losses. On the electricity side stands the total electricity demand of the object including the consumption of the heat generators – heat pumps, back-up heaters, auxiliary drives. The distinction between levels is important: useful energy is the heat actually required, final energy the fuel or electricity used, and only through primary energy factors and emission factors does this lead to a statement about environmental impact.

What is compared

For every variant the simulation reports which generator covers which share of demand, how much fuel is used for it, how many operating hours occur and what residual remains uncovered. On the electricity side, self-consumption, feed-in, grid supply and the use of storage are added. Four comparison figures are particularly meaningful: the coverage per generator, the final or fuel input, the emissions and the residual demand, which makes the limits of the design visible.

Because all variants are based on the same demand data and the same climate data set, they are directly comparable. It is sensible to change only one parameter at a time – flow temperature, machine size, storage volume, operating mode or generator order – and to observe the effect in isolation.

Reference variant

A comparison needs a reference point. A simple reference has proven itself, for instance boiler-only supply or the situation before refurbishment. Against this reference, savings in final energy, grid supply and emissions can be quantified – and later the additional investment can be related to them.

Emissions

Fuel consumption is evaluated per energy carrier with the stored emission factors; CO₂, SO₂, NO_x, CO and dust are reported. On the electricity side the saving results from the avoided grid supply. As emission factors and the electricity mix change over time, they can be maintained in the master data and should be kept up to date for reliable statements.

Presentation

The results page shows heat and electricity coverage as donut charts with the shares of all generators involved, the remaining residual as a key figure and the annual work per generator in a table. The self-sufficiency analysis compares month by month which share of electricity demand is covered directly, from storage or from the grid, and reports self-sufficiency, solar thermal coverage, thermal utilisation ratio and CO₂ savings. For your own evaluations and for variant comparison in table form, all time series can be exported as CSV files with time stamp and ambient temperature.