I first published gpvdm on the web in 2012, with the thought that it would be more useful on the Internet rather than just stuck on my hard disk where only I could use it. I also thought the more people there are in the world simulating and trying to understand solar cells the better, as this will raise our chances of humanity having a low carbon future. Since 2012 there have been over 25,000 downloads of the model. All this has been encouraging and I am very pleased people have found the model useful. This increased user count has generated an increased volume of support requests, bug reports and feature requests. I’m getting 50 or so mails a week, some questions are quite simple to answer, while others are bug reports which can take considerable time to fix. Furthermore, I am currently personally paying for and maintaining the back end servers to keep gpvdm.com on the web. Realistically, I can’t continue to commit time and money to the project at the level I have done in the past.
With this in mind, I have been trying to find ways to make the project more self sustaining. I recently added adverts to the web page as a way of helping to pay for the back end infrastructure. Although, this brought in a very small amount of money (read enough for a coffee most weeks – but not every week), it still does not cover the costs of running the project (especially when my time is accounted for). Basic things which cost money are missing from the project, for example I have not signed the binaries because I can’t justify spending the 200-300 pounds of my household budget on a certificate/key. I also badly need new dedicated hardware for building and testing the code, new windows licenses for what ever is the next version of windows which comes out. Furthermore, I would like to continue to add features to the model, these include GPU accelerated 3D FDTD code for simulation of nano particles, better ray tracing for simulating LEDs, a better cluster back end which does not need to be recompiled every time to use, extend the electrical model to being full 3D, a better 3D interface etc… the list goes on. Realistically, this can not be done without some type of funding for computer infrastructure and rent/food for myself.
I have been asking for donations on the website for a while now, both through paypal and through bitcoin, It’s a shame but, I have to date not received any money at all (0 pounds). Therefore, to ensure the long term future of gpvdm I have decided to split the model into two. From now on there will be free_gpvdm and paid_gpvdm. Free_gpvdm, as the name suggests will be available for free but will only be will be available for Linux and for the time being at least it will only get bug fixes and no new features. My plan is to offer paid_gpvdm at a very low cost, just enough to cover my costs, because I still want to make sure that anyone anywhere who wants to simulate solar cells on Windows can still do so. Also, in countries where it is difficult for people to afford the model (or to get money out of the country, Iran etc.. ), I will continue to offer paid_gpvdm for free.
Again, it is not my aim to earn any real money through this, as I have a day job, but earn just enough to pay for hardware, and justify the weekends/evenings I spend writing code. I will make this change over the next few months as and when I get time. For now I hope you continue to enjoy using gpvdm for free.