Sunday, July 30, 2017

pushing electrons

The photovoltaic phenomenon is described as photons knocking electrons out of their valence orbital and creating a net charge in a semiconductor. There are holes, and dopants, and depletion zones, but I don't pretend to understand the nitty gritty physics of it. Sure is a handy property of semiconductors.

Lots of physics research, material science, high tech fabrication techniques, and government encouragement went in to the solar panels we installed this summer.

The key here, is that once the PV cells and panels are built, they keep generating electricity from sunlight for a really long time. Big payment up front, then "free" power for years.

I know that the federal tax credit for installing residential renewable energy is phasing out over the next few years, so decided to make our move now.

We are now producing our sun driven electricity, to the tune of 4.9 kW nameplate capacity. So far, our peak output was 4.4 kW, but don't know what has to align to get the full capacity. For the year, this is prime solar weather, as the winter and spring are more cloudy.

We decided on ground mount, as we have plenty of unobstructed southern facing land, and I'd just as soon not mess with the roof unless that was a much better option. I also had initially planned to design and build the rack myself. ( maybe another blog entry on how that went down).

Here I am, driving a Bobcat skid steer for the first time, with the 24" (600mm ) dia. auger for drilling the holes for the concrete piers. I am still a terrible operator, but did not kill the guys who came to help. It helped that they were both nimble and quick on their feet.

Here are the rack columns in the concrete forms, braced and ready for the  pour. The holes are six feet deep. This rack is not going anywhere.

The design for the rack required huge piers, totaling 2.5 cubic yards ( 1.9 cubic meters) of concrete between the three of them. I looked at renting a mixer and doing it by hand, but the cost was not that much higher to order the truck, and WAY less labor.

Had to dig the trench from the array to the inverter in the barn by hand. No fun in the heavy clay mixed with large rocks. Code requires top of conduit to be 18" (450mm) below ground.

Here is the finished array, soaking up the sunshine. The panels themselves are super easy to install ( as long as the rack was put up level, straight, and plumb!), and the cabling is all premade with simple plug ends. This particular design is a single string, 350VDC output with optimizers at each panel.

Pulling the home runs, terminating, tying in to the power panel were done by an electrician. I might have been able to figure it out, but he was way quicker than I would have been, and one of the grants we are going for requires a master electrician to sign off on it.

If we decide to go off grid, we will need to spend for the batteries, as well as the charge controller and a different inverter. We are a ways off from that, as we would need to reduce our load, and really do some self reflection on how much lifestyle change we would be comfortable with.

Monday, July 3, 2017

There are more things in Heaven and Earth, Horatio..........

This concept came to my attention the other day, and got me to thinking how it applies to our present society.

Tacit knowledge is knowledge that is difficult to transfer through written or spoken methods. Some examples are throwing a ball, playing an instrument, recognizing someone's face, or kneading dough. Many, but not all examples of tacit knowledge involve physical activities or modes of expression.

Since I have recently been trying to learn to identify edible plants, and to identify trees by their bark, I  find that words just can't cut it sometimes, and when it comes to eating a foraged plant, I darn sure want to walk the woods a few times with a pro until I finally see the essential differentiators of the plant, even if I find it hard to put in to words.

In the past, tradesmen, craftsmen, artisans took on apprentices, and over time, their knowledge was transferred, but was very difficult to codify.

In our ( at least in modern western countries) economies and social networks, things have become very written and oral and much less face to face or involve mind body coordination. Petabytes of information scurry around the world, as humans communicate and conduct commerce, but what is this doing, what has it done to our psychological makeup?

How does it affect our ability to empathize, to have a grounded feel for what might be true? The subtleties that abound in perfecting any new skill help one realize that sometimes the truth is too hard to capture on paper, and that maybe there are more things in heaven and earth than are dreamt of in our philosophies?

Are our brains being stretched to the limits by so much of one kind of learning , but much less of another? Why are those skills that involve kinesthetic intelligence or hands on craft abilities less prestigious or remunerated in our society?

The future I see is one where tacit knowledge transfer will regain prominence and will supplant the current mode of explicit knowledge transfer. In fact, further, the types of skills that are considered tacit knowledge will become much more important as muscle power and local economies slowly replace our fossil fuel driven economy.

Our education system has for a long time been losing its way, and not preparing our young for the real world they will have to navigate and earn a living in. Many are sensing that now, but how will the transition happen?