Which solar simulation software should be used?
How big of a system do I need to make sure my family gets electricity even if the power grid is down? If I put money into a solar project, how much return will I get? Is it cheaper to get a diesel generator or get batteries? The real answer to all of these questions is “it depends”, but anyone can tell you that. As engineers, we hope we can provide more insight than that. In this post, we will shed some light on the tools we use to help us really address your concerns.
First up, some words on the natural follow up question - “depends on what?”. Mainly on how much sunlight your panels will receive, the environmental conditions (mostly temperature), your electrical usage patterns, and the rules imposed by your utility grid around buying electricity from you. Add in financial parameters (cost, interest rates, etc.) and you have a pretty good picture of what’s needed to go into these types of analyses. To help with considering all these complex and unpredictable factors, we use solar software to simulate systems with different configurations before arriving at the best possible answer for your question. Here, we will compare the most common solar simulation platforms such as PVSyst, Helioscope, Aurora, HOMER Pro and PVWatts.
The de facto standard amongst them is PVSyst. Despite being around for 30 years, it is still the shining city on the hill which all the newcomers aspire to. If you poke around the websites of other software companies, you can find results of “validation studies” that prove their software’s output is close enough to PVSyst for you to not need to worry. Needlessto say, if you are seeking financial backing for your solar project, you won’t go wrong with showing a PVSyst report.
Where you can really feel the age of the software is in its graphics. It is what you get when the software is designed by physicists for engineers since the latter certainly won’t mind the whole screen looking like something from the 80s. Where it gets more concerning is the 3D scene outputs which belie the hours of blood, sweat and tears needed to create them. Still, the transparency of its models and the educational help menu stand out amongst competitors. An accurate software that never pretends it is a magical black box will not be hated by engineers afterall, even if the visuals of the array make clients raise their eyebrow.
If you are looking for something more pleasing to the eye, Helioscope and Aurora are your friends. Their user interface answers the question “how many solar panels can I fit in this space?” in a very intuitive way. Aurora in particular is excellent for rooftop solar projects in the US since it offers a plethora of easily accessible features like lidar and complex roof plane modeling. If you want to walk a client through the process and show them what their building will look like with solar panels, you can accomplish this in 20 minutes with Aurora.
Where these intuitive platforms stumble is in their technical customizability. They are like the latest iPhone. Sleek and impressive, but if something goes wrong, you won’t know how to fix it. Admittedly, these errors are few and far between, and their primary focus market of residential and commercial clients generally tend to not care about technical minutiae. Still, the inability as an engineer to “open up the hood” to speak and actually fix things can be frustrating. And for larger MW scale projects where these minute technical details can create differences of hundreds of thousands of dollars, the opaque magic black box nature can be a disadvantage. Which of course is one reason why PVSyst reports still reign supreme for potential investors.
If you are instead concerned with providing electricity reliably with the cheapest mix of energy sources, HOMER Pro is what you want. This UL flagship product was originally designed for people trying to figure out how to set up cheap and reliable mini-grids, and over the years it has added other capabilities like simulating a weak grid with frequent outages. They even have offshoot software like HOMER Grid and HOMER Front, focusing on utility scale grid tied systems (PV and storage, respectively).
This mini-grid focused origin lends the software perfectly for modern day backup power concerns. If you are having trouble deciding whether or not to invest in battery storage for your commercial facility, HOMER Pro’s financial analysis tools can clearly break down costs and payback time, and even conduct sensitivity analysis for what-if scenarios. Of course, to get the full benefits, you should make sure you (or your engineers) are using the appropriate advanced modules - which also come with their own price tag in addition to the main software’s.
If you don’t know what those are, don’t worry about it…assuming you’re not an engineer of course. Myanmar is such a prolific user of HOMER that the nation was featured in a HOMER webinar. As a company based in this blackout-prone country, one of the competitive advantages we get is being able to tap into a talent pool of engineers well-versed in HOMER simulations with batteries and generators. We would be more than happy to take a look at your projects.
But while the idea of using engineers to make sure other engineers are not spewing horse baloney is a concept as old as the British empire, you might not have a spare penny to hire your own team of owner’s engineers. Or perhaps you are just a firm believer in at least understanding the broad technical strokes of your business even if technical intricacies are below your pay grade. Either way, you’re looking for PVWatts.
This is a tool developed by the National Renewable Energy Laboratory (NREL), and is devastatingly simple to use. All you need is to enter an address anywhere on the globe and system size (or draw out the available space on its map) and it will tell you what that system should produce. Now you will be armed with a “ball-park figure” to protect against unscrupulous sales folk (just remember to input the settings correctly!).
So, there you have it. Need to show production reports to a bank? Use PVSyst. Working on rooftop projects and want marketable visuals? Go with Helioscope or Aurora. Does it involve storage or multiple sources of generation (i.e. not just solar)? HOMER Pro is your friend. Wanna make sure no one is pulling wool over your eyes? Use PVWatts to get a gut check. And all these platforms are relatively user-friendly - yes, even the dreaded PVSyst. So if you give it the old college try for about a month, you can become a reasonably good user.
Of course, if it were truly that easy, we’d be out of a job. It’s one thing to know which buttons to press, and another to understand what to do with the information that comes up on the screen after you do that. That’s not even considering the fact that the list above was by no means exhaustive. What would you do if say you were located in a mature electrical and renewables market (*cough* California *cough*) and you need to take the outputs of solar simulation software and plug them into yet another platform to account for things like incentives and regulations?
Or let’s say HOMER Pro spits out a number of 3,141 kWhs of battery storage as your ideal system size. Would you know where to buy one of those (hint: you can’t…at least, not without making some weird choices)? Or know if 3,100 is a close enough number? Or frankly, know if that’s actually the correct answer or if you messed up an input somewhere?
So if you just need a number, go ahead and use what we outlined two paragraphs ago. But if you want a meaningful number, one that is a product of a fascinating interplay of numerous factors like global metal prices, how the atmosphere scatters photons, tax incentives, wheeling charges, Sino-American geopolitical rivalry, and knowing how to arrange for a generator to automatically start at 2:30 am in the morning, come to us.
Yes, that was shameless self promotion, but let’s be honest. Did you really think management was going to sign off on spending valuable engineering hours writing a fun blog if it didn’t contain the aforementioned self promotion?
