If you choose AC on the PV inputs window, you are indicating that the PV array has its own dedicated inverter, and the PV-inverter combination produces AC power. The PV array will appear connected to the AC bus in the schematic. (Make sure that you account for the cost and efficiency of the dedicated inverter when modeling the PV array in this wa

I read how Homer calculates PV incident radiation and PV output, but is there any consideration for the effect on PV efficiency as a function of angle of incidence on the solar panel? I was not thinking of the shift in spectrum during the day, but rather the absorption in the cell as the angle changes (an even reflection off the glass). HOMER

I'd like to calculate the performance ratio of a hybrid system with photovoltaic. Therefore I need the solar radiation on the PV array, that means the solar radiation incident on the PV array in kWh. In the hourly data of the simulation results I have the opportunity to plot the 'Global Solar Radiation Incident on the PV Array Monthly Averages'. B

Is it possible for HOMER to calculate clearness index from solar rad, and vice versa. How does it work? When specifying monthly solar radiation data, you need to specify either clearness index or mean daily radiation, not both. HOMER can calculate one from the other for any latitude. For details, please see the Help article ‘How HOMER Calculate

It is a multiplication factor, derived by dividing available average radiation at the Earth surface by averaged available radiation at the top of the atmosphere. Yes, that is the equation HOMER uses for the average clearness index because that is the definition of the average clearness index. The averaging can be performed over any time period

What is the Clearness Index and how is it determined? Is it accounting for air mass, or the ratio of direct beam to diffuse radiation, or anthropogenic atmospheric pollution? There’s nothing arbitrary about HOMER’s use of the clearness index. The clearness index has a very simple definition. It is equal to the global solar radiation on

Does the Daylight Savings Time have any impact on the HOMER simulations? HOMER ignores daylight savings time. It assumes all inputs are in local standard time, and all its outputs are in local standard time.

To download the resource data, first choose the location for your project on the home page in HOMER. Then, go to the appropriate resource page, in the resources tab. You can download data for solar GHI for solar PV panels, wind for wind turbines, or temperature data for considering temperature effects on PV or wind turbines. Click the button "Do

I am analyzing the influence of the PV Azimut angle on the PV Production, and in a simple case, when PV are looking to the West, I was waiting large reduction of electricity, and it does not happen. At low latitudes, particularly when the slope is far from optimal, the azimuth has less of an effect than you might think. I created the following

My understanding is that conventional commercial panels are around 12-15%. How is this modelled in HOMER? HOMER denominates the size of the PV array in terms of kW of rated capacity, not in m². The rated capacity of a PV module, which is the amount of power it produces under standard test conditions, accounts for the panel efficiency. Two mod

I think HOMER is calculating the PV array output correctly. In the DMap you sent, black does not necessarily mean zero, it just means less than 5.4 kW. If you double click on that DMap and choose the ‘fine rainbow’ color scheme (below), you’ll see that in mid-summer the PV array does produce power late into the night. But the sun is in the north

We tried to compare PV energy to PVwatts values. They are quite different. Most of that discrepancy is due to the fact that you are comparing AC energy output in PVWatts with DC energy output in HOMER. PVWatts is assuming that the AC output is 80% of the DC output, so you would have to factor that 80% into your comparison. If you are not cons

"Horizontal tracking" means that the tracking axis is horizontal. The tracking system adjusts the slope to maximize the solar radiation incident on the PV array. So the surface will be inclined, but its angle of inclination (slope) will change in time. To simulate a PV array with a horizontal north-south tracking axis, where the slope is continu

How can you input radiation or temperature values from text files, and how can you save them? You cannot input temperature data into HOMER because the model does not use temperature as an input. But you can import hourly solar radiation data from a text file. In the Solar Resource Inputs window, click "Import hourly data file" and then click

Fridge is a web service that on the HOMER website that serves up an XML file containing monthly solar radiation data for a specified latitude and longitude. HOMER hits that site when the user clicks the "Get Data Via Internet" button in the Solar Resources window. Fridge decides which data set to refer to, and HOMER just accepts whatever Fridge gi

It would be great if HOMER included links to websites that provide data such as NASA site HOMER actually does provide a link to the NASA Surface Solar Energy website. In the Solar Resource Inputs window, try clicking on the "Download From Internet..." button: If you are connected to the Internet, clicking that button will cause HOMER to req

I have to make some changes in HOMER for analysis using a flexible photovoltaic panels? HOMER can model a flexible PV panel if it is installed on a flat surface so that it has a single orientation that you can describe with a single slope and azimuth. But if the panel wraps around some structure so that different parts of it point in different

As we know, a-si thin film pv module has quite a different behavior from c-si pv modules. The pv efficiency depends on the sun irradation intensity and incident angle of the sun beam. We would like to know if HOMER can model these effects. HOMER does not account for the effects that you mention. It assumes that the efficiency of the PV array v

I'd like to model 2 DC bus, is this possible? You can do exactly that by modeling the PV array and its dedicated inverter as an AC PV array. To do that, you need to: 1. Set the output current to AC in the PV Inputs window. 2. In the PV Cost Table and Sizes to Consider table, where you specify the rated capacity of the PV array, s

I do notice on the plots of daily power that the PV power shows shoulder at the beginning and end of the day. Where does that come from? The problem is that HOMER assumes you are entering global horizontal radiation in the Solar Resource Inputs window, so it resolves it into its direct and diffuse components (using the Erbs model) before it do

How do I model with multiple numbers of inverters, different inverters for solar PV, and battery? The way to do it is to specify the PV array as being connected to the AC bus rather than the DC bus. Then what HOMER models as the PV array is actually the PV array and its dedicated inverter. What HOMER models as the inverter is the "other" inve

The PV I-U curves (I-U versus temperature, Irradiations, and Under standard conductions) cant be indicated in PV inputs. As I could understand from the program, derating factor is the alternative. But how could the user estimate the Derating Factor from I-U curves? HOMER assumes the PV array is outfitted with a maximum power point tracker (MPPT

Do you have another suggestion for considering shading? Unfortunately HOMER cannot model shading very precisely. Your approach would work quite accurately if HOMER allowed you to specify direct and diffuse radiation in each time step, since shading affects the direct radiation much more strongly than the diffuse radiation. But HOMER does not

HOMER uses a very simple model of the PV array. It assumes the PV power output is linearly related to the global radiation incident on the panel, regardless of temperature. A panel rated at 5 kW puts out 5 kW at an incident radiation of 1 kWh/m2. HOMER assumes that it will put out 2.5 kW at an incident radiation of 0.5 kWh/m2. I know that thin

Unfortunately HOMER cannot simulate the system without the MPPT. Please look up 'MPPT' in the index of the Help system for more information.

You might have noticed that the PV slope and azimuth are not decision variables so HOMER won't optimize them the way it optimizes the size of the PV array or the size of the battery bank. But you can use sensitivity analysis to find the optimal orientation of the PV array.

I wonder how HOMER takes into account the efficiency of the PV panels. Could you tell me more about that? PV panels are rated according to how much power they produce under standard test conditions (incident radiation of 1 kW/m2 and a particular temperature, which I forget). HOMER always deals with the PV array in terms of rated kW, not in m2.

I was using HOMER to explore the difference in PV output when you change the orientation of the PV array when I got some unexpected results. The NE orientation gave more output than the north facing array (using a southern hemisphere situation). In looking at the detailed data exported from the program the Plane of Array solar radiation for the N

I want to do a PV run in Homer. At the input screen for PV capacity, it isn't totally evident to me if the input should be gross DC capacity of the array or net AC output capacity after accounting for I^2R losses in the wiring, inverter losses, dirt buildup losses, and degradation over time. From the help system, theformula for output that is red

I am confused how to make sensitivity analysis of PV cost, and compare this with the diesel cost i. e the the impact of each other when price increse or decrease. I try to make this but the PV cost multiplier is confusing me. IF I use PV cost as sensitivity variable then the COE will become very high. Would you please tell me how it works. The

HOMER uses that variable only to calculate the PV cell temperature, and the cell temperature has only a slight effect on the PV power output. So it makes sense that the PV energy production changes only slightly with changes to that efficiency input. If HOMER made you enter the PV array size in m2, plus the PV efficiency, then you would expect th

How would I fix the PV kWh annual output or efficiency from the kWp? I cannot see how to change the 13% efficiency for a generic cell for example or how to fix the kWh annual basis. For my project location, 1.5MWh for a 1kW cell is a good rule of thumb and I want to make this the generic option. I then want to create a sensitivity to shading to red

Can you tell me what HOMER assumes for the solar panels for effiency? And when using the monthly averages in the solar resource data, is HOMER assuming continuous power or does it take into account no sun at night at all? Unless you are modeling the effect of temperature on the PV array, HOMER doesn't ask you for the PV array efficiency. You

I am trying to model a solar panel and vary the panel efficiency as well as area. How does this correlate to Homer PV inputs of size(kW)? For example if I want to model a 1 meter squared array with an efficiency of 23 percent how do I represent that in Homer? If the PV panel efficiency is 23%, then under standard conditions (1 kW/m2 of radiati

Why doesn't the generated PV power follow average available energy, when moving from the Equator to the North Pole? Great question. The "average daily radiation" is actually the "average daily radiation on the horizontal surface". The output of the PV array depends on the radiation striking the PV panel, not the radiation striking a horizonta

The met data I had was for north facing, latitude inclination i.e. 38 deg. so this is what I used. I converted Mj to kWh (/3.6) and the figures appear similar to others for this part of the world i.e. Victoria. Like California we are among the worst bush fire prone areas in the world. Our scientists have predicted due to climate change bush fire

The replacement cost occurs when the component needs replacement. Your PV array and your wind turbine both have a lifetime of 20 years which is the same as the project lifetime, so neither requires replacement. For that reason, HOMER won't use the replacement cost of those components so you can leave them at zero. To see how HOMER uses the repla

I don't seem to get any different results between non tracking and horizontal tracking with monthly adjustments. The meaning of vertical vs. horizontal axis tracking is often a point of confusion in HOMER. Maybe some of that confusion is in play with you system. Telling HOMER that your PV is on a horizontal axis with monthly adjustments means

HOMER now models the effect of temperature on the PV array. If you check the temperature checkbox in the PV Inputs window, you can enter the temperature coefficient of power and the nominal operating cell temperature. Then you have to enter temperature data: either monthly values or from a time series data file. You can import solar radiation an

A maximum power point tracker is a solid state device that exposes the PV array to the DC voltage that maximizes its power output. HOMER assumes that the PV array is being controlled by an MPPT because in most cases it is, and because modeling a system that lacks an MPPT is more complex and much slower. The ‘tracking system’ that appears on HOMER

We did not find out how to chose different technologies (such as monocristalline silicon, polycristallin silicon, thin film) for the PV Array. Is this possible? If not, could you please tell us which technology is used for the calculation? HOMER models the PV array with some basic assumptions just a few parameters, such as rated capacity, derat

Where could I find that HOMER resource data? To download resource data from the HOMER website, you'll have to sign in with your email address and password, then click on Sample Files in the Download section of the navigation bar at the top of the screen. You'll get a drop-down box from which you can choose to download TMY2 solar data (hourly ra

Now that HOMER Pro can model dedicated inverters for PV arrays, I am wondering what number to enter in the search space. Should I use the DC kWp value of the array? First of all, you can check the box "Match parameters to PV". In the future this will be renamed "Ignore dedicated converter". You can still assign the PV to the AC bus, but the inver

For any latitude, one can precisely calculate the mean extraterrestrial solar radiation (the radiation striking the top of the atmosphere) for any month of the year. HOMER does that. So when you enter the monthly mean radiation at the surface, HOMER immediately divides that by the mean extraterrestrial radiation to calculate the clearness index.

I am interested in part of the Solar resource and scaled data. I do not understand how HOMER scales data with Graham algorithm, more exact, how it knows how to scale hourly data? And if you could me explain a little more about graphs of scaled data PDF, scaled data CDF, and scaled data duration curve. HOMER scales hourly solar radiation data in

Hourly result Table there are two coulms namely solar radiation and incidence solar.It means we have to use solar radiation data as input and Homer will convert it into icidence radiation according to the slope,latitute,longitute of the site, wherefrom the data are collected In that table, the ‘solar radiation’ is the global solar radiation on

I have no clue where to find the clearness ratios needed for HOMER to give me solar radiation values. You can enter solar resource data into HOMER by specifying either radiation values or clearness indices. You specify one and HOMER calculates the other. Look up 'solar resource inputs' in the index of the Help system for more information. Th

Is there information about what internal models are available in HOMER for the estimation of daily solar radiation series on an inclined plane, based on hourly average data? From the hourly data of global solar radiation on the horizontal surface, HOMER calculates the hourly global solar radiation on the inclined surface using the HDKR model.

The issue of scaling the solar resource data is independent of the PV array. By "fixed location" I mean a particular latitude and longitude, but especially latitude. The latitude has a strong effect on the amount of solar radiation received at a site, but at any particular latitude, what determines the quantity of solar radiation received at grou

It is easy to get solar resource data into HOMER via the Internet In the Solar Resource Inputs window, enter your latitude and longitude, then click Get Data Via Internet. If you are connected to the Internet, that button retrieves monthly solar data for the specified latitude and longitude from NREL's and NASA's satellite databases. Give that a

For the horizontal axis, continuous adjustment tracking option, you can set the axis of rotation to whatever you want. For an east-west axis of rotation, enter an azimuth of zero degrees. For a north-south axis of rotation, enter an azimuth of 90 degrees. (The azimuth will actually switch between 90 and 270 degrees as the sun crosses overhead at

Does the program include the possibility of simulating Solar Thermal (Trough/Tower) Generation? HOMER does not simulate solar thermal generation. It can model a thermal load that can be served by heat recovery from generators and/or excess renewable electricity but not by solar thermal generation.

If I change longitude 80° to 86° and keep the same time zone GTM-5, is it valid? The latitude matters a lot in HOMER’s solar calculations. You can see it in many of the PV-related equations that appear in the help file, for example in the article labeled “How HOMER Calculates the Radiation Incident on the PV Array”. But the longitude and the

Can HOMER model solar hot water? No, HOMER can't model solar water heating.

Why does your program show the pv generating during evening hours? Further, the program tells me that my data is higher than atmospheric data… location 22 Deg South and 72 W. Did you create that solar radiation data with HOMER? It looks shifted one hour, at least if I'm right that the time zone is GMT-4 like mainland Chile. I used HOMER t

I suppose the right data are the temperature for the daytime, actually the average temperature during the hours of energy production. Am I right? You are right that the most relevant ambient temperature data is for the hours of PV energy production. So if you enter just a single value per month, a conservative approach would be to enter the a

Is the time zone important to set? HOMER’s time steps are based on civil time, so the load, the grid price, the wind speed is all specified in civil time. But the sun operates on solar time, and HOMER needs the longitude and the time zone to convert between the two. So yes, the time zone is important.

Products: HOMER Pro and HOMER Grid I set the PV to 182KW capacity. The derating factor is set to 80%. The inverter is not considered. However, the PV output showed a maximum PV output of 185kW. Could you explain the results? There are several reasons why the output of the PV is higher than the rated number. The rated power of solar panels is d