Our extraordinary spring continues with long, sunny April days burning away raw memories of a cold, harsh winter. With each day, I ponder at the wasted photons striking my roof and the pennies that could have been gathered from them. Now I will have to wait a while longer.
When I received my quote from Installation Company, they specified a SMA SB3000 inverter, and like many would, I immediately hit the web to find out more. It turned out that the number in that designation, 3000, referred to its power rating and this one was rated at 3 kW. This seemed strange because the array of panels I was ordering are to have a peak capacity of 3.5 kW. I wondered whether this underspecification was intended as a way of keeping costs down.
Solar photovoltaic systems generate direct current (DC). Like a battery, they have a positive and a negative terminal and the electricity from them flows in only one direction. However, the power systems within our homes and factories work using alternating current (AC). Here the electricity flows first in one direction and then in the other, swapping polarities and back again fifty times a second. It is the job of the inverter to convert the DC power from the panels into AC that can work with the domestic supply, and it will do so in sympathy with it - making sure that positive and negative are the right way round at the right time. As it does so, it has to be able to handle the amount of power being generated by the panels.
For most of the time, a 3 kW inverter would be absolutely fine. Given cloud, seasonal sun or times of the day when the illumination is not optimum, there is almost no time in the year when my system will generate power at its peak capacity. That can only occur when the Sun is shining through a clear sky at an exactly perpendicular angle to clean panels. My first guess was that Installation Company had figured there was no need to supply an inverter rated to match the array for this very reason. I brought it up with my contact within the firm and he took the opposite view. The 3 kW inverter was wrong and it should be a more muscular version, the SB3300. In fact, there may be a time of year, in the early afternoon on a sunny June day, that the illumination on the panels might just stretch the ability of a 3 kW inverter to do the job.
Today, I decided to see if Installation Company had a firm date for my panels to be installed. The lady's answer was that their supplier was having difficulty sourcing the correct inverter and the signals were that the units wouldn't arrive until the latter half of May. That seems to put the installation back about 4 weeks from when I had hoped. The good news is that I can afford to wait longer for the bureaucracy behind my loan application to do its stuff. The bad news is mild frustration and the thought of a zillion more springtime photons landing uselessly on my roof.
One interesting sidenote is that while the SB3000 is rated for a peak of 3 kW, the SB3300 will handle a peak of 3.6 kW, more than enough for my system. Another fascinating nugget for this gadgetboy is that the inverter can have a Bluetooth interface which allows it to be monitored remotely, and to a very high extent; heaven for someone like myself who loves monitoring systems. A little remote display called the Sunny Beam will keep daily reports of the power from the panels and will pass that information into my computer via USB. Oh, heaven! It will even draw little histogram graphs to show how the generation of power was distributed over a day. I'll investigate this more later.
No comments:
Post a Comment