Funding

Funding for open source PV modeling software may be categorized by funding source (public or private) and by funding kind (direct or indirect). Here, we define direct funding as resources that are specifically allocated for developers to support or create an open source tool. In contrast, we define indirect funding as resources that are used to support or create an open source tool in the process of achieving a larger goal. Next, we provide examples of each combination of funding source and kind. Public/Direct: DOE EERE supports development and maintenance of PVLib Matlab and SAM. Public/Indirect: EERE initially funded the PVPMC and its workshop, which features open source tools and thus indirectly supports open source PV modeling tools. Private/Direct: Southern Company Services and the Electric Power Research Institute funded UA developers to contribute a forecast module to PVLib Python. Private/Indirect: Developers at companies such as SunPower and First Solar have used PVLib to conduct research that furthers their businesses. Developer time spent reporting issues or contributing to the software is an indirect funding source.

A challenge for open source software is that direct funding for it is inconsistent. This is especially true for funding that goes towards maintaining existing functionality rather than adding new features. Indirect funding of open source PV software has enabled packages such as PVLib Python to receive minor, regular updates. Whether or not indirect funding is sufficient for the long-term health of a project is an open question.

Funding agencies demand to know the impact of their awards, however, it can be difficult to accurately quantify the impact of an open source software project. This is especially true if the project is used by or incorporated into additional projects. The developers of many of the tools described here have made efforts towards cataloging their impacts but are often able to report only statistics indicating interest, such as numbers of downloads and webpage views. To our knowledge, there is no comprehensive public repository with this information for open source PV tools.

Most public funding for open source PV modeling software has been through the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy. EERE proposals often require data management plans that describe how a project’s data, including software code, will be disseminated. EERE’s data management plan instructions suggest open source and websites such as GitHub as acceptable methods to disseminate results. Funding agencies could provide further indirect support for open source software by explicitly encouraging open source by-products of funding.

Some users of open source PV tools may be interested in providing relatively small amounts of funding to sustain or improve the tools that they use. However, many of the lead developers of the projects discussed here are employed by government labs, universities, or large companies. Contracting with large institutions can be difficult, and this effectively creates a minimum contract value that is often more than a single user can contribute. We suggest that the open source PV tools developers explore alternatives such as spin-off companies focused on open source development, utilizing intermediaries such as the Numfocus organization or donations through a university foundation, and micropayment methods such as Patreon.