One of the limit I have noticed is that, in case of biogas co-firing, it seems not to be possible to keep the engine running if biomass becomes too expensive with use of natural gas for example, whereas it is the case if biomass becomes unavailable (natural gas consumption increases). You are right about the co-fired generator. HOMER will alway

What exactly is the Energy Charge on the Simulation Results – Grid page? HOMER assumes your monthly utility bill consists of two parts: an energy charge, which is what you pay for the kWh you consumed, and a demand charge, which is what you pay for the peak kW demand in the month.

When using the option of connecting to the grid, when HOMER does its optimization run, it includes the cost of the converter for the grid-only option, even though the load is AC, and thus the converter serves no purpose and should not be included in the cost (i.e. the COE for the grid only case should be the grid rate). Isn’t this right? HOMER

Demand charges can be specified in the grid component. Demand charges are determined by multiplying the peak usage in a month by the demand charge specified under the "Rate schedule". If you have two (or more) demand charges specified during a month, those will be independently calculated and summed for the month based on the peak usage for each

The net present cost of grid extension has two components. The first component is the net present cost of buying power from the grid over the project lifetime. The annual cost of buying power is the power price times the total annual electrical demand, and you divide that annual cost by the capital recovery factor to find the net present cost. T

Where is the grid inputs window that should have grid price, sell back rate etc? Click the Add/Remove button at the top of the schematic, and look for the Grid section in the bottom left corner of that window. Choose the radio button that says “System is connected to grid”. Once you close the Add/Remove window, the Grid button will appear in

Could you why there would be an O&M cost for the grid? HOMER reports the cost of buying grid power as the “grid O&M cost”. If the system you are modeling consists of a wind turbine and the grid supplying an electric load, the system probably meets the load partly with wind power and partly with grid power. The cost of buying that grid

For some reason I don't understand, HOMER seems to prefer using energy from the grid even if I force it to use an electrolyzer and a fuel cell and there is enough excess energy available to refill the hydrogen tanks ... I thought the optimization was based on cost saving and not using grid energy should be cheaper than using it. no? Yes, HOMER

The grid reliability tab is new for version 3.2, which will be released in late April. We accidentally shipped the version 3.2 help file with version 3.1.4. We're sorry for any confusion this caused. You can simulate random outages in 3.1.4 with real time rates mode, but it's a little less intuitive. See this article: http://support.homerenergy.co

For purchase and sales capacities, what should the input be on sales capacity and purchase capacity? The sale capacity is the maximum amount of power the system can sell to the utility grid. The purchase capacity is the maximum amount of power the system can purchase from the utility grid.

What is the difference between off-grid and mini grid? We call a system ‘grid-connected’ if it connects to a regional distribution network of several thousands of megawatts capacity. Such a network will typically connect thousands or millions of electricity consumers together, served by large and distant power plants. An example of a grid-con

Why is there an initialization phase with a complete unloading and loading phase of the battery? HOMER uses economics to operate the dispatchable power sources. In your system, you have two dispatchable sources: the battery bank and the grid. The price of grid power is simple: $0.10/kWh. The price of battery power is a little more complicate

On the Rates page of the Grid Inputs window, a radio button at the top of the page lets you choose between scheduled rates and real time prices. Choose real time prices, and then click the button labeled "Import Real Time Price Data". The file must contain two columns (the first for grid power price and the second for the sellback rate) and 8760

The fundamental principle on which HOMER's simulation logic rests is the minimization of cost. Whenever it has the choice between two or more dispatchable power sources (batteries, generator, grid) it chooses the power source or combination of power sources that can supply the load and the required operating reserve at the least cost. That concep

The maximum grid demand parameter on the Advanced tab of the Grid Inputs window will force the generator on whenever the net demand (Load - renewables) is greater than that value. HOMER may choose to run the generator more than that if it is cost-effective to do so. Another option would be to schedule the generator to run for certain hours using

What is the best way to model intermittent grid supply, for example, in India where the grid is running 10 hours per day? Make sure you are updated to the latest version, 3.2.1, which you can do here: https://users.homerenergy.com/pages/homer_pro_update You'll also need the advanced grid module. You can model this grid a few different ways. Firs

I'd like know if HOMER will consider the electricity feed-in (the government incentive to use RES) during the simulation with PV and wind generators. On the Rates tab of the Grid Inputs window you can specify the sellback rate, which is the value that you receive for power you sell to the grid. You can set that to a high level to reflect the f

HOMER currently assumes 100% availability (excluding resource limitations) for every component, including the grid. We plan to change that in an upcoming version of HOMER, but until then here is a work-around to model an unreliable grid. Create a generator and label it as the “grid”. To do this, set the "grid" generator to have description "Grid"

If grid reliability is the real issue, then I suggest you model the grid as an unreliable power supply. The way you do that in HOMER is to represent the grid with a generator as described in article 10463 You can then schedule the generator to be off for a few hours a month. The attached sample file demonstrates. You can keep your diesel genera

According my testing, I found the battery only supply load when there is not grid connection, is this correct?? No, that’s not correct. In any time step in which the renewable power cannot meet the load by itself and the system must generate power from some dispatchable source (i.e. run a generator, buy grid power, or discharge the battery) H

HOMER can model grid extension in a simple way, and compare its cost with the cost of a stand-alone system. To model grid extension, click the "Add/Remove" button and choose ‘Compare stand-alone system to grid extension’. Then a button labeled "Grid extension" will appear below the schematic. That button brings up a window where you can enter th

Can I simulate different grids, different regulation strategies for building (system)-grid interaction i.e. : 1. Regulation strategy: the building cannot sell the energy at any time it wants, but this is regulated by the utility when it is possible 2. Regulation strategy: utility requires from the building that the fed back energy sh

How can I specify (using HOMER) different sellback prices for photovoltaic and wind turbine? HOMER does not allow different sellback rates for different power sources.

For a mathematical explanation of net metering, please look up 'grid outputs' in the index of the Help system. The punchline is this: without net metering, your power bill is equal to purchased_energy * power_price - sold_energy * sellback_rate. With net metering, your power bill is equal to (purchased_energy - sold_energy) * power_price. Does

The "maximum grid demand" input (on the Advanced page of the Grid Inputs window) does allow you to simulate peak-shaving systems. For example, if you are simulating a grid-connected microturbine serving a load that peaks at 100 kW and you set the maximum grid demand to 75 kW, the microturbine will operate any time the load exceeds 75 kW because HO

Can HOMER Pro model a system that uses energy storage (batteries, pumped hydro, etc.) for peak shaving? Peak shaving requires the Advanced Grid module. Some rate structures include a demand charge based on the highest power you purchase from the grid. Reducing the highest peak(s) of grid purchases can reduce the demand charge. You can set up peak

In New Mexico the public service company, PNM, allows net metering AND purchases each kWh of power generated. It doesn’t seem that there is a way to model this with HOMER, is this correct? I think what you mean is that PNM pays some non-zero amount for net excess generation. You can indeed model that with HOMER. For example, imagine that with

I would like model a grid connected system without reverse power flow That is already possible with HOMER simply by setting the "maximum grid sale" to zero kW. That means HOMER will not allow any power to flow from the system to the utility grid. If the grid-connected system produces more power than is required to meet the electric load, the

I have designed a system connected to the grid with renewable sources and electricity storage. Sometimes the renewable output exceeds the electrical consumption. Therefore, the system has two options: Sell the electricity back to the grid Store the electricity I do not know how HOMER chooses between these two options. Sometimes it wo

HOMER can model a range of grid-connected solar photovoltaic (PV) systems. These include those with feed-in-tariffs, net metering, as well as resilient solar + storage systems that ensure electricity even when the utility grid goes down. Grid-connected PV systems can operate under a range of different tariff structures. The HOMER Pro Wizard is a g