Interview with Chief Developer Henk Oldenkamp

Old­enkamp is not only one of the pio­neers in solar ener­gy, his impact on the indus­try is great – in Nether­land and beyond. His fas­ci­na­tion for solar ener­gy start­ed at a young age, but the tech­nol­o­gy was still in its infan­cy when he was con­script­ed in 1982. There he got out of that by arrang­ing a job with the wind ener­gy group at the Eind­hoven Uni­ver­si­ty of Technology.

“I devel­oped, among oth­er things, soft­ware and elec­tron­ics for test­ing wind tur­bines”, Old­enkamp explains. In 1984, I start­ed up a com­pa­ny in that field. But PV con­tin­ued to attract me. The turn­around came in 1992 dur­ing a con­ver­sa­tion with Wim Sinke, at the time already the face of the dutch solar ener­gy com­mu­ni­ty. At that time, the small­est pos­si­ble PV sys­tems still cost tens of thou­sands of guilders. The invert­ers were at least 5 kilo­watts. He said, “Actu­al­ly, we should make those very small, prefer­ably one invert­er per solar pan­el”. I said: “I can do that. I’ve always been very good at that.”

Old­enkamp put his mon­ey where his mouth is. His first micro-invert­er came onto the mar­ket around 1996, in col­lab­o­ra­tion with Shell Solar and cable man­u­fac­tur­er NFK. In total, some 80,000 units were installed, which at the time was a lot. How­ev­er, the ship was to sink soon after. NFK was tak­en over by DRAKA and received a new man­age­ment. “I had almost com­plet­ed the next gen­er­a­tion, but was dis­missed from one day to the next like a thug, I had to hand in the keys. Lat­er some resid­ual mate­r­i­al was put on my doorstep, but that was it. That fick­le­ness was also seen at Shell Solar, which sud­den­ly left the Nether­lands in 2003 with the mes­sage, that things would nev­er work out here. The gov­ern­ment went along with this ridicu­lous sig­nal; the sub­si­dies for PV were stopped at once. So, it often blew with all the winds along. When Philips start­ed mak­ing invert­ers, they put a lot of tax mon­ey because ’if it is Philips then it must be good‘. In ret­ro­spect, it all turned out to be point­less. I was fed up with it.”

The Ger­man com­pa­ny SMA bought the tech­nol­o­gy of Old­enkamp in 2009 and attract­ed him as a con­sul­tant. But that com­pa­ny pulled the plug on its micro invert­er busi­ness. Old­enkamp had to start all over again, and took his future into his own hands. Togeth­er with Julian Matthe­is, he found­ed Solar­na­tive and took the next step in minia­tur­iza­tion of his tech­nol­o­gy with the JT-350. “It took me years, this is a real break­through. The secret lies in the switch­ing fre­quen­cy. The high­er that is, the small­er you can make it. You can trans­fer small­er ener­gy pack­ets. The down­side, how­ev­er, is that with­out inno­v­a­tive mea­sures, effi­cien­cy will drop. I man­aged to raise the res­o­nance fre­quen­cy up to 1,000 kilo­hertz, while it can deliv­er 350 watts to the grid. This allows us to make a microin­vert­er that fits into the frame of a solar pan­el. An impor­tant advan­tage is the lifes­pan. A met­al frame of a solar pan­el dis­si­pates heat and is usu­al­ly between 15 and 20 degrees Cel­sius cool­er than the solar pan­el. This also applies to an invert­er that you put in. As a result, its life is extend­ed by a fac­tor of 2 to 3.”

Anoth­er advan­tage of the JT-350 is accord­ing to Old­enkamp, that it is cheap. It is clicked direct­ly into the frame, that saves cables, con­nec­tors and work. There are also no bypass diodes required. All this also makes it safe. The occur­rence of an elec­tric arc is impos­si­ble. The mains volt­age is sep­a­rat­ed from the solar pan­el volt­age by a dou­ble safe­ty insu­la­tion. This elim­i­nates the risk of elec­tro­cu­tion in the event of dam­age to the solar mod­ule. The gate­way has an auto­mat­ic map­ping func­tion that deter­mines the order of strings and any miss­ing con­nec­tors. It is also in direct con­tact to the Inter­net via Long Term Evo­lu­tion (LTE) tech­nol­o­gy. The LoRa in the gate­way pro­vides wire­less com­mu­ni­ca­tion with oth­er devices. Data cables are there­fore not required, and it is pre­pared for appa­rats in a smart ener­gy household.

Old­enkamp: “At Inter­so­lar Europe we received orders for 1,000 units per month, while pro­duc­tion has not even start­ed yet. Our own fac­to­ry should be up and run­ning, prob­a­bly in Frank­furt. Then we will soon be putting hun­dreds of thou­sands away. The installers are already lin­ing up. This has part­ly to do with what we call bal­cony PV here. In Ger­many it is per­mit­ted to plug PV sys­tems up to 600 watt peak direct­ly into the wall sock­et. This is now also per­mit­ted in Aus­tria, Spain and Poland. The rest of Europe will prob­a­bly fol­low soon. This devel­op­ment will give Solar­na­tive a kick­start. Our tech­nol­o­gy fits per­fect­ly. I have want­ed this for 30 years, and now I’ve done it. I am final­ly going to fin­ish the sto­ry and that feels real­ly good.”