FAQ

When using a Conversion Technology with multiple Input Energy Carriers, the resulting Output Energy Carrier Efficiency doesn't make sense

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The efficiency is always expressed with respect to the Primary Input Energy Carrier.

How can I share a project with another user?

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All projects can be easily shared by selecting the options menu of the project by clicking on the three dots. There the option “Send Project Copy” is presented.

The total irradiation displayed in the Sankey diagram for the year does not sum up to the yearly irradiation of the select solar profile multiplied by the solar surface area.

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The capacity of the solar installation (and therefore the surface on which it is installed) depends on the results of the optimization. The Sankey diagram only display the irradiation on the chosen surface by Sympheny's optimization engine. Hence, if a scenario does notconsider the installation on the maximal surface, the irradiation valuevisualised in the Sankey diagram will only account for the irradiation receivedon the installed surface

How can the second optimal solution be found?

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In practice a study sometimes requires evaluating how well other few options are performing even though these are not optimal – e.g. for assessing other criteria than costs or emissions.

The most efficient way to do what you propose in the current software is:

> Create a "Scenario" including the full set of technologies that you would like to consider.

> Copy this Scenario and modify the technology set (e.g. by removing technologies) to create a reference scenario to be compared with the first.

> As necessary, create additional reference scenarios as a basis for comparison.

> Execute all the created scenarios simultaneously.

The optimal emission solution has excessive life-cycle costs compared to the other ones (when battery is included)

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If no maximum battery capacity is defined, it is likely that the emission optimal solution models the battery storage as a seasonal storage, which is not the desired pattern. It is the case for example when the battery’s grey energy is not taken into account.

In order to keep the battery within a reasonable range, its capacity should be capped. In the Web-App, under Supply Technologies > Storage Technologies Candidates, you can edit the maximum capacity of your technology.

For an even more holistic consideration of the emissions, the embodied CO2 of the technology can be added. With this the CO2 minimization option will be more realistic

State of Charge (SoC) does not reach maximum or minimum

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If in the SoC of a storage technology never reaches 0, this is because the maximum charging/discharging rate is defined as a percentage of the total storage capacity.

In the Web-App, under Supply Technologies > Storage Technologies Candidates, you can edit the maximum charging / discharging rate of your technology. You can also set up a maximum storage capacity, to make sure that your storage capacity (and therefore its maximum charging and discharging rate) is limited.

What is the difference between optimal design and optimal operation?

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Optimal design shows the best technologies that can be installed -chosen by Sympheny optimization engine- and their best size in kW.

Optimal operation shows the optimal operation of the chosen technologies in kWh

Error message "Model was proven to be either infeasible or unbounded"

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This error message occurs in situations in which the scenario is setup in such a way that there is no feasible solution.

This error often comes from the fact that the energy flows can not be balanced due to the model set up. This can be the case when one technology has multiple outputs and that this results in an ‘overproduction’ of an energy carrier, which cannot dissipate during a certain specific hour.

How is the annualized life cycle cost calculated?

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As the optimization period of Sympheny is one year, the costs/revenues 2 to 5 (energy cost, fixed and variable O&M cost and income) are assumed to be constant ona yearly basis.

The investment costs (in k CHF/year) however are derived from the capital cost (ink CHF). To annualize the costs, the capital recovery factor is used. Symphenyassumes an endless operation, therefore the annualized capital costs(=investment cost) are considered as the sum of the annualized capital costs ofeach technology (depicted with the letter t) (with its own life-cycle N(t) and therefore CRF(I,N(t)):

Annualized capital costs =                              

The capital recovery factor is a ratio used to calculate the present value of an annuity (= a series of equal annual cash flows).  It can be understood as such: A loan of amount A with a interest rate of i% can be paid back with N annual payments of A * CRF(i,N).

with i= real discount rate(Input step 8 in Sympheny):  

i’=nominal discount rate(=the rate at which you could borrow money), f=the expected inflation rate

N(t) = life cycle of technology t

Note that the interest rate inputtedby the user in step 8 on the Sympheny WebApp (=i), can include or not theinflation rate (in which case it is assumed that f is 0) (see equation above)

The maximal energy produced by my technology is higher than the capacity given in the system diagram

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This is because the capacity given in the system diagram represents the capacity of the (selected)primary output, while the output given in the load duration curve is the combined outputs (in this case cooling and waste heat).

How can I control the type of electricity (e.g. grid’s electricity vs. renewable electricity from PV) that my heat pump is using as a ‘first choice’? Can I give a priority to one input?

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Within a multiple input system, we cannot give apriority to an input: indeed, the priority is a parameter of the optimization.

However, when it comes to the best solution in terms of CO2, it means that it will always favour renewable electricity over grid electricity (assuming the grid has a higher CO2 intensity than the renewable electricity, which in most of the cases is true, except e.g. if you have a very clean electricity from the grid and an on-site production with PV and batteries with high grey energy).

When it comes to the best solution in terms of Cost, if the optimization has chosen to install the PV and as long as the price of buying the grid's electricity is higher than selling renewable electricity, it will maximize the internal use of renewable electricity automatically, and will choose renewable electricity (from your PV) over the Grid's electricity for the Heat pump.
If installing a PV system is too expensive for the cost optimal solution, you can force it's installation.

What does "Demand Sale Price" mean?

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The demand sale price is the price an end user has to pay to use the energy.

Sympheny thus calculates the 'Import price' as a cost for the site owner, and the 'Demand Sale Price' as income.

In the sense of a site owner looking at the whole lifecycle costs, the Demand Sale Price then naturally reduces his/her project costs.

Why are solar resources entered twice? Once for Energy carriers and again for Solar resources?

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The energy carriers only define theenergy flows that are considered and used in the hub. The energy carrier onlyopens the generic energy flow, the detailed characteristics are then defined inthe solar resources step.

The input for onsite resources definesthe area of the plant, as well as the installation profile of the plant at itslocation.

Both inputs are necessary to ensurethe use of solar energy.

Can the heat pump and chiller also be installed as a bivalent system?

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Yes it is possible to adjust the network, either use the water heat as an energy carrier or it is also possible to include entire anergie nets to ensure the waste heat is used in an optimal way.

Error message "Pre-installed solar capacity (kW) of "Solar PV, roof installation" exceeds maximum possible power (solar Area * solar specific power)"

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To solve the issue, the efficiency of your solar technology must beequal or higher than the implicit efficiency. Calculate the implicit efficiency(= kWp/area/1) and modify the efficiency given in the technology for this value(rounding up).

E.g. for a PV area of 3’500 m2 and 500 kWp, the minimalefficiency to allow for the 500 kWp to be installed is 14.3%.

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