PV Design Software and the Cloud

 

 

 

 PV Syst is one of the most complex PV performance and financial model design tools in the industry. It's one of the first commercially available PV design packages - initially written for small off-grid systems in Europe, then evolving into more complex software that is capable of precise output design of utility scale projects. PV Syst is arguably the industry standard globally and is both loved and hated by the professional PV designers who use it every day. PV Syst has seen a gradual erosion of its position by free and web based offerings (below) and, in response, has made an effort to enhance its offering, which is currently in version 5.

 

Some of the new features that will be available in the sixth version of the PV Syst software, to be released within a few months, include: (i) direct search of a location using Google map; (ii) direct shading calculation during the simulation (avoiding interporlation uncertainties) – figure 1; (iii) new outputs such as “irradiance shading loss” and “electrical shading loss” position; (iv) improved project management parameters access copy, templates – figure 2; and (v) for PV modules – Sandia model implementation and comparison – figure 3 and tools for parameter optimization (low-light, I/V curve). 

 

Key features: Preliminary design, Shading analysis, 3-D project design with geographic solar orientation, technical output analysis, economic and financial analysis, geographical solar insolation

 

 Price: ~$1050 USD 

 

 

 

 

 Developed by NREL, it’s the most advanced and commonly used performance and financial tool in the USA. The software is not only designed for (residential, commercial and utlity scale) PV, but also other renewable technologies such as dish-stirling CSP, solar-water heating, small and large wind and biomass projects.  The SAM UI looks and feels like a government project. The designers at NREL have taken the stodginess of PVSyst and PVSol and updated their 1980's Volvo functionality to the 1990's Cadillac level excess. The awkwardness of the design is a good thing - it proves that SAM was made by PhD level engineers! Despite feeling clunky to use, SAM is a fantastic tool - providing almost endless tweaks and customizations to get your overall model right where you want it - plus, it's free. 

 

SAM can provide performance predictions and cost of energy estimates for grid-connected power projects based on installation and operating costs and system design parameters that you specify as inputs to the model. The current version of the SAM includes performance models for the following technologies: (i) Photovoltaic systems (flat-plate and concentrating); (ii) Parabolic trough concentrating solar power systems; (iii) Power tower concentrating solar power systems (molten salt and direct steam); (iv) Linear Fresnel concentrating solar power systems; and (v) Dish-Stirling concentrating solar power systems.

 

SAM includes several databases of performance data and coefficients for system components such as photovoltaic modules and inverters. For those components, you simply choose an option from a list. SAM can also automatically download data from an online database of retail electricity rates and structures for U.S. utilities. For the remaining input variables, you either use the default value or custom. Some examples of input variables are: (i) Installation costs including equipment purchases, labor, engineering and other project costs, and land costs, and operation and maintenance costs; (ii) Numbers of modules and inverters, tracking type, derating factors for photovoltaic systems; (iii) Collector and receiver type, solar multiple, storage capacity, power block capacity for parabolic trough systems. (iv) Analysis period, real discount rate, inflation rate, tax rates, internal rate of return target or power purchase price for utility financing models; (v) Building load and time-of-use retail rates for commercial and residential financing models; (vi) Tax credit and payment incentives amounts and rates.

 

SAM displays modeling results in tables and graphs, ranging from the metrics table displaying levelized cost of energy, first year annual production, and other single-value metrics, to the detailed annual cash flow and hourly performance data that can be viewed in tabular or graphical form. All graphs and tables can be exported in various formats for inclusion in reports and presentations, and also for further analysis with spreadsheet or other software. Did we mention that this is all free?

 

 Graphs and Charts on the Results page displays graphs of results that you can easily export to your documents. 

 

 SAM's performance model makes hour-by-hour calculations of a power system's electric output, generating a set of 8,760 hourly values that represent the system's electricity production over a single year. 

 

SAM's financial model calculates financial metrics for various kinds of power projects based on a project's cash flows over an analysis period that you specify. The financial model uses the system's electrical output calculated by the performance model to calculate the series of annual cash flows. SAM includes financial models for the following kinds of projects: (i) Residential and Commercial Projects; (ii) Power Purchase Agreement (PPA) Projects; (iii) Levelized Cost of Energy and Cash Flow (levelized cost of energy (LCOE) after-tax cash flows for projects using retail electricity rates, and from the revenue cash flow for projects selling electricity under a power purchase agreement); and, (iv) Incentives (the financial model can account for a wide range of incentive payments and tax credits).

 

 Key features: Preliminary design, technical output analysis, economic and financial analysis, geographical solar insolation, Free.

 

Price: Free. If you pay taxes in the US, then you have helped to develop this tool. 

 

 

Solmetric software was written to support the Solmetric SunEye site survey tools. Like the SunEye firmware, it appears to be written in some form of Visual Basic and/or Windows Mobile; it's not pretty. If visual quirks can be tolerated, the PV Designer is a noteworthy and useful tool. The Solmetric SunEye was the first site survey device to take the steampunk style Solar Pathfinder and drag it into the 20th century by essentially adding batteries and the ability to capture and edit shading images. PV Designer goes one step further by coding the whole process and facilitating the editing and reporting of shading results.  Many designers forgo the PV Designer product and import the SunEye data directly to SAM, PVSyst or others.

 

Designed particularly for residential and commercial roof projects where the user can drag and drop solar panels on the user-interface, it includes worldwide solar panel and inverter database, in addition to Solmetric’s weather data. 

 

Key features: Preliminary design, shading analysis, technical output analysis, economic and financial analysis 

 

 Price: $400 USD, but you need the $2000 SunEye to generate shading data.

 

 

 

A web-based application that is designed for residential and commercial PV projects. Its easy to use interface and monthly subscription method makes the Solar Design tool a very attractive option.  The Solar Design Tool is developed by Derek Mitchell, a Silicon Valley engineer based in Santa Cruz, CA. 

 

The UI in Solar Design Tool is pure Web2.0+; clean, fast and with almost constant updates. Module and inverter lists stay current as does weather data with no annoying downloads to wait for. 

 

One of the most valuable aspects of this tool is the convenient ability to quickly generate both preliminary designs and fully fleshed ones. Some software require tiresome forms and cross checks just to see if a string size works - that is not the case here.

 

Key features: Preliminary design, drag-n-drop module on roof, weather data, technical output analysis, web based collaboration with several users

 

Price: $7- $25- $45 per month. Free trial available.

 

 

 

Skelion is a bit of an outlier here, being a Plugin for Trimble SketchUp. The use of SketchUp became very popular during the blossoming of the solar industry in Europe due to its powerful 3D graphics and easy use. The 3D warehouse of shared models fostered the development of solar component designs and Skelion took the process a couple of steps further by automating the population of PV modules onto a roof surface, then running a basic PV Watts production calculation.

 

  Simple to use; just select a surface where the solar panels will be inserted and click on the solar cell icon. A menu appears that asks you about tilt and orientation for the panels, the type of panel, and a shading range for a given day. Photovoltaic panels can be selected from its own database or you can create your own, and they can be placed in portrait or landscape orientation. After that, the plugin automatically inserts the solar panels on your selected surface. It also works with irregular surfaces.

 

 

Helpful information about the use of Skelion and its features can be found in the videos available in its website (http://skelion.net) and in also its blog, which contains several relevant topics related to the design of photovoltaic system in general.

 

Price: Free, limited version and $133 USD pro version.

 

 

The tools surveyed have some notable differences, but they can all be used effectively in modeling PV output and presenting the results. It will be interesting to see if the older software suites are encouraged to look beyond a static Windows Only market. Apple Computer, for instance, has about a 10% share of the workstation OS market, but it could be argued that they are a growing concern and should be considered as a viable project design platform. Regardless of operating system, the Cloud is likely to emerge as the most logical place for installing design software that is dependent on a dynamic range of products and specification.