Making Raspberry Pi in the woods

So the Ohmsteader is an old school DIY kinda guy, and so it’s taken him a pretty long time to come around to adding computer control to his DIY projects – but no more.  The wonderful and amazing Raspberry Pi and its even more spare cousin Arduino are changing that.  Full fledged and surprisingly easy to play with computers/micro-controllers that cost in the neighborhood of $30 and are open source and fully hackable.

The Raspberry Pi turn one year old on the imaginary February 29, 2013 (this is what happens when you release on a leap day!) – and more than a million units have been sold in that time with an advertising budget of right around zero dollars – just incredible!  Apparently all people needed was to be told you can have the computer that sat on your desktop just a few years ago for 30 bucks and it just about the size of a credit card now to decide to start playing with them (count me in that category).

The tech embracing self proclaimed environmentalists over at have come up with a list of Raspberry Pi projects worth making happen.  Some of these are novel (building an upcycled carboard case for the computer on a single circuit board), while others are very Ohmsteader check out in particular the DIY home automation controller (e.g. dim your lights from your mobile phone, or control your thermostat remotely).  But perhaps the most interesting to me is the idea of running the Raspberry Pi off-grid – a PV powered RPi (“Arr-Pie”as they’re called in shorthand).  Because these devices run on DC they’re very easy to integrate into offgrid systems.  Attached to an offgrid battery system you can now have home automation for things like internal lights and lighted walkways for less than the cost of a family dinner out.

The Ohmsteader is only just getting started with Raspberry Pi and Arduino, but there are several projects ongoing so keep watching for updates!

Grid Parity – Part 2

In the previous post we started to define grid parity by talking about how much it costs to supply electricity to your house. The other half of the equation that defines grid parity is how much it costs to make your own electricity. As with all things related to the electricity industry there is no simple answer.

Perhaps the most important factor to consider when thinking about how expensive it is to make your own electricity is that storing electricity is expensive by most standards. Once you add storage to an equation the cost of supplying electricity can get pretty expensive – to be certain, the price of storage is going down, especially as billions of dollars in R&D are being invested by and for the auto industry as it electrifies – but it’s easier to think about grid parity if we think about electricity that is consumed as it is produced.

So, if we are not storing electricity, we can focus on the cost of production. There are three main factors that allow us to determine how much it costs to make electricity:

- Fixed/capital costs

- Variable/O&M costs

- Financing costs

Most folks will agree that these are pretty much universal factors in assessing the cost of anything. In the production of electricity there is a great deal of variation in the ratio between these numbers. As an example you can buy a relatively low cost gasoline generator but your price of fuel (a variable cost) will be very high, or you can buy a PV panel with a relatively high fixed cost and no fuel costs. If you don’t have enough cash to pay for those fixed costs up front, you need to consider the financing costs.

If you’re connected to the grid it is not cost effective to make your own electricity from a gasoline generator – the fuel costs are just too high. Conveniently, you can make electricity from resources that have low or no variable costs such as wind or solar – their fuels are essentially free, and that makes it easy to calculate the variable costs – let’s pretend they’re zero to keep thing simple.

It turns out that calculating their fixed and financing costs is pretty easy: The cost of the product (and any money borrowed to buy it) divided over the lifetime output of the product. For a typical solar generation system the fixed costs have been falling pretty rapidly and are now down under $.15 per kWh.

That number happens to be right around the price of electricity you might buy from the grid and that’s what we call grid parity.

When you consider that some resources, like solar, are what they call “peak coincident” (they produce electricity when the demand for electricity is highest) they do even better.

Grid Parity – Part 1

In this post and the one that follows we’ll talk about what the term “grid parity” means in two easy to understand posts.

Grid parity is a pretty interesting concept. It’s a lot like peak oil in that once you understand the term you begin to see a lot of things very differently.  A great part of the philosophy that underlines much of the thinking here on is driven by the concept that once people see it’s not in their best interest to let someone else make electricity for them, they will make it themselves.  Grid parity is actually a key ingredient of that mix.

The term grid parity consists of two words:

Parity – meaning equal to.

Grid – meaning the price of buying electricity from “the grid”.

That’s pretty much it – grid parity is the point in time when making your own electricity costs the same as buying electricity from a utility.

Of course, it’s a bit more complicated than a single sentence, so let’s talk about what those two pieces mean in greater detail:

Electricity is provided via a grid of interconnected wires with some fancy (and not so fancy) bits of equipment in between. Because there is not a lot of creativity in the electricity market that grid that delivers the electricity is called the “electricity grid”.  These are sometimes called transmission and distribution infrastructure (transmission generally refers to very big very long wires that run sometimes hundreds of miles and distribution refers to smaller, shorter wires like you might see attached to poles in your neighborhood).   It turns out that all those wires and transformers and things cost money, which should not be that surprising considering that they run not only to every single power plant in the country (and a good number outside of the country) but also to almost every single home, apartment, farm, shopping center, and street lamp in the country.

Even with all that infrastructure there is actually no electricity flowing on it until someone pays to actually make some, so you have to add the cost of making electricity in there too.

Adding those two things together gives you the cost of electricity delivered over the grid.

That cost is passed on to you via rates that vary by customer class, location, and a host of other factors.  Rate design is very complicated, but let’s just assume that rates are designed to cover all the costs of supplying electricity based on how much electricity you use.  Once you have that you have half of the equation, the other half (the cost of making electricity on your own) we’ll cover in the next post.

What’s so wrong with small scale ground mounted solar?

I recently looked into ground mounted vs. rooftop solar for a family member and was really surprised by the difference in permitting costs of all things.

For a small, residential sized system the permitting costs dwarfed the savings associated with a ground mount system right out of the gate – they were literally thousands of dollars more.  For my relative this was a deal breaker, which is pretty unfortunate because there was plenty of nice, unshaded level ground that he was willing to turn over to electricity production.

It turns out the problem, at least in California’s central valley is based in the idea that any ground mounted PV system is going to be a “for profit” business rather than a residential program designed to offset one’s own electrical load.

Our original idea was to build a carport that also made electricity.  It seemed simple enough.  Some shade to park under and lower electric bills thrown in for good measure.  But now our original plan may be to build a carport and then, separately, put PV on its roof.

I’ll be sure to post updates in this process when I have them to share, but until then I’d love to hear of any similar problems folks have had and creative solutions to them.

Across the country (the long way) in a Tesla S

This is actually not something I would have thought was possible, but it turns out that the miracle that is the KOA campground is the easiest to find electric vehicle charging station – whoda thunk?

This rather enjoyable blog features a young couple’s journey from the SF bay area, where they picked up a Tesla S, to DC where they dropped it off – just to see what would happen.

What are the two big takeaways?

1) Well, it CAN be done.  Right now. This month even.

2) The solutions to some perceived problems may come from corners you aren’t even considering.  KOA as a “gas” station. Need I say more?

Obviously not everyone would try this hard, waiting around for a 110v outlet to make it to the next real charging facility would be pretty soul crushing for anyone in a hurry, but I am pretty sure EV denser areas won’t have a recognizable different for gas vs. EV vehicles in the next decade.  It turns out that there’s electricity almost everywhere.

-The Ohmsteader

Grid Connected Vehicles as Mobile Generators

The folks over at  have a nice article on plug in electric vehicles that also generate electricity for the grid.

The article is about PG&E, no small owner of fleet vehicles, and their interest in bootstrapping Chevy-volt like technology for range expanded EVs that rely on an on-board electrical generator.

Their after market to the after market mod of a Chevy Silverado is, apparently, designed to bring 125kW of grid deliverable capacity in the form of an on board battery and a generator.  At $100K these aren’t cheap trucks, but they are designed to help power whole neighborhoods, not individual houses.

The cool thing is, the same reasoning applies to a car like the Volt, or really any electric car with a large enough battery that you can run your house off of for a few hours and still drive to work the next day with the remaining charge.

While PG&E thinks about this issue in terms of supplying power when traditional power plants aren’t online, there’s no reason why the technology can’t apply to folks who would just rather buy their electricity from their neighborhood solar battery charging facility or whatever people will think of as common sense when gasoline costs $20 a gallon.

-The Ohmsteader

Welcome Ohmsteaders!

As you may or may not know, the Ohm is the scientific measurement of the unit of resistance, r.  It’s a pretty big deal.


So when it came to naming a blog site I had a hard time beating having ohm somewhere in the mix.

As it happened I realized that resistance is a big part of the equation – without someone actually taking a stand and saying “actually, this is how I think it should be” we were going to end up with a pretty undesirable outcome.  So here’s a place where ideas and information get to be free.

The Ohmsteader blog is about being free to get out there and do – perhaps to make mistakes, but to be better off for it.

There will be a lot of cross posting from other blogs I contribute to, and news articles I find worth sharing, but also examples of how I’m making a go of it in the world of DIY power.


Ask questions – I promise I will answer.