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Program workflow

This page describes the complete working sequence in EPOS-Plan, from creating the project to evaluating the results – in more detail than the Documentation, which presents the scope of functions in overview. The order is a recommendation: you can switch between the areas at any time, but every stage uses the results of the previous one.

1. Starting the program and basic settings

After starting, EPOS-Plan shows the main window with program name and version in the header and the menu bar with Projects, Administration and Help as well as the language switch. Before the first project it is worth looking at Administration › Settings: directories for import and export, the path to the VDI 3805 manufacturer data, the address of the online documentation and the interfaces for climate data and place name search. The master data catalogues – building types, hot water and process profiles, electricity consumers, heat pumps, boilers, CHP modules, collectors, PV modules, storage, climate regions and energy prices – are also reached through the Administration menu. Factory data sets are write-protected; own entries are created alongside them.

2. Creating or opening a project

A new project is started via Projects › New or the tile on the start page. The wizard first asks which building blocks the project contains. This selection controls the further sequence – building blocks that are not ticked are skipped and do not appear in the simulation configuration later. It can be changed at any time via Projects › Edit.

On the second page you enter project name, person in charge, client and a description and select the climate region. Project name and climate region are mandatory. The wizard then leads through the activated building blocks; “Save” writes the project and all assignments to the database.

An existing project is opened via Projects › Open – the list shows name and description – or directly through the entry for the most recently edited project. Deleting a project removes all associated data and is therefore protected by a confirmation prompt.

3. Defining the climate region

Every project is assigned to exactly one climate region providing ambient temperature and irradiance for all 8,760 hours. If no data set exists for the location yet, create it in the climate data management: enter the place name or the coordinates and start the import. EPOS-Plan determines the geo-coordinates, downloads a typical meteorological year, converts the irradiance to the orientations south, east, west and north and calculates the solar positions. Two charts show temperature and solar angle profiles for checking. On the start page you select the region and save it, which creates a project-specific copy.

4. Determining the heat demand

Heat demand arises from up to four components that are recorded separately and added hour by hour. The first is building space heating. Select a building from the catalogue – filtered by residential or non-residential use, building type and construction period – and transfer it to the project. In the project copy you enter the reference quantity, usually the floor area.

If consumption data are available instead of areas, select oil consumption in litres, gas consumption in cubic metres or megawatt hours, or general fuel consumption. Together with the annual utilisation ratio of the old plant EPOS-Plan derives the useful heat and scales the building model so that it produces exactly this demand – the annual profile stays physically based while the annual total matches the bill.

The characteristics of the building type can be maintained in the catalogue: floor area and area per user, room height, window areas by south, north and east/west, window transmittance, areas and U-values of external wall, roof, ground floor and other components, thermal bridge supplements with their connection lengths, air change rate and construction type. A second page holds the usage conditions: set room temperature, night, weekend and holiday setback, maximum room temperature and four holiday periods. From these inputs the program calculates the daily heat load for each of the 365 days and distributes it to hourly values via a type-dependent 24-hour curve.

The second component is domestic hot water: select a type from the catalogue and enter the annual consumption – distribution over the year is handled by monthly shares and a weekly profile with 168 hourly values that can be edited day by day. The third component is process heat, recorded in the same way, with a separate entry for every temperature level or process. The fourth is an externally imported heat load profile added directly as an hourly series. In addition network losses are entered as a percentage or an absolute annual figure and distributed evenly over the year.

5. Determining the electricity demand

Electricity demand is built from consumer types with monthly values and 168-hour weekly profiles. Because self-consumption and storage management would come out systematically too favourable in hourly averages, EPOS-Plan works internally with 35,040 quarter-hourly values per year. If a measured load profile is available, import it – hourly as well as quarter-hourly values are recognised and superimposed on the calculated profile.

6. Selecting and sizing the heat generators

Heat pump. In the selection dialogue you filter the catalogue by manufacturer, operating principle, control, design, installation, existing back-up heater, flow temperature range and rated output. After transferring it, you define flow and return temperature, the handling of the back-up heater, the bivalent operating mode and possible lock-out periods. Decisive for the result is the performance map: for the selected flow temperature it holds heat output and coefficient of performance for every source temperature, between which the simulation interpolates hour by hour.

Boiler. Selection by fuel type and capacity class; rated output, fuel-dependent efficiencies, condensing flag and standby loss are stored. An electric boiler is modelled by selecting electricity as the energy carrier.

CHP. Selection by fuel and thermal capacity class with thermal and electrical output, overall efficiency and lower modulation limit. The operating mode – heat-led, electricity-led or without feed-in – is set in the result area and can be compared directly there.

Solar thermal. Collector type, number of modules, aperture and module area as well as tilt and azimuth. Yield calculation uses the collector characteristics according to EN 12975.

Photovoltaics. Module type, number of modules, tilt and azimuth; several sub-arrays for different roof surfaces are possible and often useful in practice.

7. Defining the storage

Thermal buffer tanks are described by volume, flow and return temperature and standby loss; the usable capacity follows from volume and temperature spread. In the next step you assign the tank to one or more generators and define the thresholds for charging and switching off. Battery storage is described by capacity, power and state-of-charge limits; in the simulation it absorbs surpluses and later covers the residual electricity demand.

8. Configuring the simulation

The Simulation configuration dialogue is the control centre. Four selection fields determine which heat generators take part – heat pump, boiler, CHP and solar thermal – and one field each applies to photovoltaics and battery storage. The order of the fields is the priority: the first generator covers as much demand as possible, the second gets the remainder.

In the buffer tank section you assign the storage to the selected generators and define flow and return temperature as well as switch-on and switch-off thresholds. The overview on the right shows all selected generators with the associated plants of the project. For heat pumps you set further properties there by double-clicking: the priority with several machines, the heat source – ambient air, constant temperature, buffer tank, own source profile from monthly and weekly values or an imported CSV temperature profile –, the heat sink – total demand, hot water only or space heating only – and the operating mode: runtime-optimised at maximum output, output-optimised with exactly the required amount of heat, or PV-optimised with priority for self-generated electricity. The configuration is saved with the project.

9. Running the simulation

On start, EPOS-Plan calculates the year in hourly steps on the heat side and in quarter-hourly steps on the electricity side. The starting quantity of every hour is the heat demand; the first generator covers as much of it as performance map, operating limits and storage level allow, the residual heat goes to the next. What remains open appears as residual heat demand. In parallel the electricity balance is kept: the consumption of the heat generators is added to the demand of the object, CHP power, photovoltaics and storage discharge are subtracted; the remainder is grid supply, negative values are feed-in.

10. Evaluating the results

The evaluation is structured by area. Energy demand shows heat load and electricity demand as an annual profile or load duration curve with maximum and annual total, the heat load separated into space heating and hot water. The heat pump area reports heat coverage, bivalence point, storage capacity, average full-load hours and minimum peak boiler output, plus profiles for demand, back-up heater and production, the electricity consumption, the output over ambient temperature and a module table. Corresponding areas exist for boiler, CHP, solar thermal and photovoltaics with coverage, production, residual demand, consumption and emission figures.

The results page summarises everything: two donut charts for heat and electricity coverage, key figure tiles for the remaining residual demand, a table of the annual work per generator. The self-sufficiency analysis compares direct use, storage contribution and grid supply month by month and reports self-sufficiency, solar thermal coverage, thermal utilisation ratio and CO₂ savings. Two further views show heat and electricity production as annual profiles with generators and storage level that can be shown or hidden. The result can be saved per project, and all time series can be exported as CSV files with time stamp and ambient temperature.

11. Recording costs and creating reports

Only once the technology is settled is it worth recording costs, because then the quantities are fixed. The cost module is divided into investment, operating and energy costs: positions per component with amount, unit, service life and a range between favourable and unfavourable case, with the plant costs stored in the technical module available as a planning value. For energy prices you maintain working, standing and demand price, calorific values and emission factors with a validity date for every energy carrier.

On this basis EPOS-Plan assesses the comparison group of base project and variants by the net present value method in accordance with DIN EN 17463: net present value, annuity and present values per project, replacement investment and residual value as well as three scenarios for the expected, the best and the worst case. The base project is the reference; against it, net present value difference, dynamic payback period and internal rate of return are reported. Sensitivities show how sensitively the result reacts to the discount rate and the energy price escalation – each varied by one percentage point – and to investment and energy costs with a deviation of ten per cent each. Also taken into account are the bonus rules of the German CHP Act (KWKG) 2025, the CO₂ levy under the German Fuel Emissions Trading Act for fossil fuels and an electricity matrix of high and low tariff for winter and summer; the emission balance compares combined and separate generation and reports the amount of CO₂ avoided. How the calculation is built up in detail is described by the subpages Economic analysis, Revenue calculation and Emissions.

The report forms the conclusion. Variants are created from the base project via Projects › Save as variant…; in the dialogue Projects › Variants/report you select the projects of the group and put together the sections of the document. Every report run first simulates all selected projects afresh, then calculates the economics of the whole group and only afterwards produces the output – a Word comparison report with charts and difference tables as well as an Excel workbook with the same figures, both without an Office installation. For three projects around 35 seconds are to be expected. Details are described by the subpage Creating the report.

Notes for practice

Check the demand against known consumption data before adding technology – a demand that is twenty per cent wrong devalues every subsequent design. Calculate a simple reference variant, for instance boiler only, to have a basis for comparison, and add components one by one so that it remains traceable which building block contributes what. Worked cases are collected under Examples, the engineering background under Fundamentals.