Tuesday, December 13, 2011

What Are Your Real Fuel Costs?

I recently wrote and made a Rotary Club presentation about using compressed natural gas (CNG) in vehicles. I drove one of our freshly converted CNG powered Ford Escapes with me to demonstrate. Part of the process was to calculate fuel amounts and costs and to compare those costs with the cost of conversion to CNG. I’ve done exercises like this before but for some reason I seem to forget a startling fact: if you keep a vehicle until it is dead or mostly dead, to about 200,000 miles, you spend quite a bit more on fuel than you do on the purchase price. Imagine how it would influence car-buying decisions if that number was first and foremost on the minds of consumers; perhaps even posted along side the vehicles MPG information?

Our 4-cylinder Escapes average a respectable (but not great) 25 miles per gallon. At $3.90 per gallon (probably a low average for the next few years), we could spend $31,200 each in fuel alone on these vehicles. Our large service vans or our dump truck get about 16 MPG. We could spend $48,750 each in fuel over the lifetime of these vehicles. Because we will convert them to CNG, our actual costs will be less than half of that. The switch I made from a 19 MPG Dodge diesel pickup as my personal vehicle to a 40 MPG VW Jetta Sportwagon diesel is saving over $20,000. That is practically the cost of the car.

The initial cost of the Hybrids and plug in electric vehicles seem high. If you are in it for the long haul, though, they are a good deal
. The difference in fuel costs between the 28 MPG standard Toyota Camry and the 41 MPG Hybrid Camry is $8,832, considerably more than the difference in the purchase price. Still, the benefit drops the higher the MPG of the comparison vehicles. The difference in overall fuel cost between a 49 and 50 MPG vehicle is just $318 where the difference between 15 and 16 MPG vehicles is a whopping $3,250. This is why it is not difficult to understand the number of diesel Sprinter service vans in use by businesses (we have two). If you can average 21 MPG instead of 14 MPG for a comparable van, you’ll save $18,571.

So, the next time you look at buying a car or truck, think about the total cost of the vehicle, not just the purchase price. And please ask your favorite local elected officials to think about this as well. I’d like our taxpayer money to be spent effectively.


Sunday, December 11, 2011

Paint 'Em White

That is one item on Bill Clinton’s list of 14 Ways to Create Jobs. He is talking about roofs on buildings. Our Secretary of Energy, Dr. Steven Chu, has been talking up the clear benefits of white or reflective roofs. When making a roof material and color choice on a new building, this is a no-cost way to significantly reduce the energy needed to cool buildings. Zip. Zilch. A white roof does not cost more than a black one. And when in the process of replacing a roof on an old building, it does not cost more to install a white roof. Again, not a penny more.

In commercial buildings in the southeast, most of the conditioning load is to cool the building. Because of internal heat generation from lights, people, and machines, cooling systems are often running even whe
n it is cool outside. This is another reason why a reflective roof choice is so effective in our climate. It reduces the load of the primary mode of operation of the mechanical system.

We chose a white metal roof for our commercial building in Durham. We chose it because it looks good, because it is extremely durable, because it is a great surface for collecting rainwater that we will use for irrigation and for flushing our toilets, and because it has the highest Solar Reflectivity Index (85) of any roof that met the rest of our design criteria. Not only does this save on utility costs over time, it allowed us to install smaller systems to condition the building. Yup, the color of the roof saved us money before we received our first utility bill. Why isn’t this the primary color choice for roofs?


Pictured below: The low-sloped white roof of the ClearSense building at 502 Rigsbee Avenue overlooking Downtown Durham. The rails will support solar panels (soon to be installed).

Thursday, December 1, 2011

Solar Panels: That Simple?

When installing solar panels, you stagger the rows so that one row of panels does not shade the next. And, of course, it makes sense to tilt them towards the sun. That simple? Nope. Throw in a few more factors like limited area for the array installation, the limitations of the rack systems, the relative cost of more and less efficient panels, and the surprisingly small reduction in efficiency if the panels are not at the optimal angle to the sun and another, better route emerges.

For the array that we are installing on our commercial building in Durham, we made choices that yield a cost-effective solution but that seem counter-intuitive. While slightly more complicated than this, our options boiled down to two alternatives that both exceeded our energy generating goals. Option one: expensive and highly efficient panels installed in consistent and optimally tilted rows. Option two: a larger quantity of considerably less expensive and somewhat less efficient panels installed mostly in consistent and optimally tilted rows but with two leading rows that are not tilted towards the sun. In fact, they are tilted slightly to the north. The lack of tilt allowed us to install the first rows more compactly without shading the next row. We picked option two. Option two delivers slightly more power. Option two saves over $40,000 in up-front costs. Not bad. Our only concern is hearing the comment: “Hey, Mr. Solar Intelligence, the sun is to the south.” To those folks, I’m happy to tell this story, enjoy the clean energy, and put the money in the bank.

For any energy geeks (this term used endearingly) reading this, the first rows of panels are on a separate inverter so the reduced output from these rows does not degrade the output from the optimally tilted rows. Option two schematic roof panel layout shown below.