Monthly Archives: June 2014

Solar PhotoVoltaic Primer

The cost of photovoltaic systems (panels and inverter) has dropped to about 2 to 3 dollars per watt. At this price systems have payback times in the 10 to 15 year range, regardless of size. This assumes a cost of about 10 cents a kilowatt hour (kW-hr) for electricity.

Here are a number of nuts and bolts issues for those interested in solar power. First and foremost you must have a location with southern exposure. Even a small amount of shade can seriously reduce energy production. For most this means a roof top location, but it needn’t be if you have the space to put the array on the ground. The simplest mounting puts the panels flat on the roof. The pitch of the roof is not all that important as long as it faces south.

sun's path

sun’s path

The amount of space needed for an array of course varies as to how much total power you want to produce. Different manufacturers make panels in different sizes (watts) but the total space needed is the same because all PV panels have the same efficiency, about 15 %. Five 100 watt panels will take up the same space as one 500 watt panel. One kW requires about 80 square feet of space.

A big decision is whether the array is isolated or connected to the electrical grid. Grid-tied systems here in Arkansas can take advantage of net metering. This means that the power produced by the panels can actually make a meter run backwards if they are producing more power than the home is consuming at any time. About the only disadvantage of a grid-tied system is that when the line goes down, so does the solar power production. This is necessary to protect power line workers.

PV Grid-tied system

PV Grid-tied system

The alternative to grid-tied is to go entirely off line by buffering production with batteries. This avoids the aforementioned problem, but greatly increases the cost and “hassle factor” of the system. This is only practical when connection to the grid is cost prohibitive, as in remote locations.

The total amount of energy produced by a system is obtained by the total wattage of a system. For example a 1 kilowatt system can produce a maximum of one kilowatt hour only when the sun angle is ideal. Averaged over a year, a simple rule of thumb is that you can get 4 hours of net production per day. Hence a 1 kW system can be expected to produce 4 kW-hrs per day, more some days, less others.

Let’s use an average consumption of 1000 kW-hrs per month (close to the average in Arkansas) to determined a system sized to replace 100 % of electric needs. 1000 kW-hrs per month means 33 kw-hrs per day. Divide that by 4 to get a a little over 8 kW system. To allow for some inefficiencies say we use a 9 kW system. At 2.5 dollars a watt, the total cost would be 22,500 $. The 30% federal tax rebate brings the final cost down to 15,750 $. Sales taxes and installation will add to the cost, but these numbers can be used to approximate a cost if you are interested in going solar.


Arsenic Anyone?

A popular talk show doctor recently had several brands of Apple juice tested and claimed to have found Arsenic. Whereas nobody wants poison in her food, the question of the amount and its relevance is important. First a little background on Arsenic.

One of the first things that come to mind in association with Arsenic is poison. And indeed it is poisonous. It has been used as a pesticide because it is generally poisonous to all forms of life, rats, cockroaches, even some fungi succumb to it. Ironically it is also known to be an essential trace element for some organisms and possibly humans in tiny, tiny amounts.
Arsenic has been known since antiquity and is poisonous to varying degrees depending on its form. As important as the potency of a poison is the amount of the poison. A seventeenth century physician-chemist by the name of Paracelsus famously proclaimed “everything is poisonous, nothing is poisonous, the dose makes the poison”. One example is lima beans which naturally contain toxic cyanide ion, but lima beans aren’t toxic as the dose of cyanide is too small.
Arsenic has historically been a component of intrigue. In 15th century Italy the Borgia family waxed powerful. Lucrezia and Cesare were among the children of Cardinal Rodrigo Borgia (who became Pope Alexander VI- obviously things in the church were different in those days!) Lucrezia was said to be a very effective poisoner as she had learned how to concoct lethal Arsenic potions which were undetectable in food or drink. Arsenic-laden wallpaper
Napoleon may have been done in by Arsenic, but not by an intentional poisoning. His villa on the island of St Helena had wallpaper colored with Sheele’s Green, a pigment made from Arsenic. In moist air a mold can grow on the wallpaper and convert the Arsenic to a volatile form. It appears at least for Napoleon that not the butler but rather the wallpaper did it. Another Arsenic pigment called Emerald Green may have impaired the health of Cezanne, Van Gogh, and Monet among others.

Emerald Green Paint Pigment

Emerald Green Paint Pigment

Some women in the Victorian era would eat small amounts of Arsenic to produce a pale complexion. Tanned skin in those days indicated that one worked in the fields and was therefore of a lower class.
Now back to Apple juice. Any Arsenic in juice is an issue if for no other reason that juice is a mainstay of many children. Two questions come to mind. Where did the arsenic come from and is there enough Arsenic in the right form to be a risk to health?

 Generally speaking the Arsenic is coming from the soil in which the fruit is grown. It can be in the soil naturally or due to use of Arsenical pesticides applied to the soil. Lead Arsenate was used in the United States until the seventies. Arsenic is very stable and could persist in soils for many years. Another source may be China, where environmental regulations are lax at best. Over half of the Apple juice sold in the United States now comes from China.

The amount of Arsenic measured recently in some of the juice samples does exceed the World Health Organisation’s suggested limit for safety. However the method of measurement included both toxic inorganic and relatively nontoxic organic Arsenic. When only the toxic form is considered the level appears to be safe. The FDA has been monitoring arsenic in Apple juice for decades and sees no threat to public safety based on these findings.

Pollutant Emissions and Efficiency

The answer to the question in the real estate business about property is always “location location location.” Similarly, the answer to the energy utilization question is always “efficiency, efficiency, efficiency.”

Dr. Amory Lovins, a physicist and energy guru coined a term for it called the “negawatt.” A negawatt as opposed to a kilowatt is the energy you don’t use by being more efficient. Negawatts save rather than cost money, yet still provide the same service to a homeowner.

So why all this talk about negawatts and efficiency? The Public Service Commission (PSC) here in Arkansas will soon have to address new regulations, promulgated by the Environmental Protection Agency (EPA) intended to reduce the harmful effects of power plant emissions.

These rules will impact coal fired power plants most directly, and rightfully so. Burning coal for electricity generation releases the largest share of pollutants from any of the possible fossil fuels. For a given amount of energy produced, burning coal produces more Carbon Dioxide, Sulfur and Nitrogen Oxides, heavy metals, fine particulates, etc – all serious pollutants.

You might ask that if we throttle back the burning of coal and coal is cheap, then our cost for electricity production is going to go up. Not necessarily for two important reasons. First, the cost you see on your electric bill is only part of total cost.

The cost of impaired health due to exposure to the aforementioned pollutants is real but not accounted for. Likewise, the cost of environmental degradation from global warming is real. The cost of political instability due to global warming induced climate change is real. The Less coal we burn, the lower are these external costs born by society.

So how do we contain the directs costs? The second step is demand side management. Now we’re back to negawatts. The new EPA regulations call for lowering carbon emissions by 30% by 2030. We need to achieve about a 2% reduction per year to meet the standard. It shouldn’t be difficult to achieve this goal through efficiency improvements alone.

Nobody really cares how many kilowatt-hours they use, what they care about is having a warm in the winter, cool in the summer, well lit home. The less energy you need to achieve that goal, the lower will be the electric bill. A very cheap step is to check that ALL incandescent lights have been replaced by compact fluorescent bulbs, or even better now, Light Emitting Diodes.



Consider adding some solar panels to produce energy and lower the electric bill. The cost of PV systems has decreased drastically, 60% in just the last two years!

Check the attic to see if more insulation is in order. How old is your HVAC system? Newer equipment is much more efficient. If you have an older Heat Pump, newer is better, i.e. more efficient. Or consider a ground source heat pump which is much, much more efficient.



Some of these these efficiency upgrades can be expensive, but recent legislation can help. Most notable is the PACE law. The Property Assessed Clean Energy bill allows cities and/or counties to form Energy Improvement Districts which have the authority to assist homeowners to make improvements, the cost of which is then added to the property taxes at such a rate that the increase in property taxes is matched by a corresponding decrease is energy costs.

Efficiency, Efficiency, EFFICIENCY.


Crowd Sourcing Energy Storage.

The amount of electricity produced for the grid must be matched very closely with demand. There are large swings in demand from hot summer days when demand is high to mild spring and fall nights when demand is low.

To match demand with supply requires that a certain amount of power be constantly produced, the so called base load, and this must be supplemented with additional power sources for peak demand times. The cost is higher for electricity generated only intermittently. To encourage use of electrical energy during off peak times and discourage use during peak times some areas vary the cost of electricity with the season and time of day.

If massive batteries were available the power production could be smoothed out and only base load would be needed. Excess power produced at night could be stored for use when peak demand occurred. Alas such massive grid connected batteries don’t exist. Or do they?

Instead of a few massive batteries for a metropolitan area, how about 10s or 100s of thousands , even millions of smaller batteries all interconnected to the grid.

Enter electric vehicles as battery storage devices for the grid. The idea is called V2G, for Vehicle to Grid. Electric car batteries are connected to the grid for charging and this is especially true at night, so they immediately help to level demand by charging off peak. An electric vehicle owner could charge at night at home then drive to work in the morning. There, the driver would reconnect to the grid and charge or discharge as needed. Smart outlets controlled by computers could simply shuttle power to and from the individual vehicles as needed, essentially crowd sourcing energy storage and delivery.

Especially valuable would be plug-in hybrids and fuel cell vehicles. In addition the the energy stored in their batteries, they could act as stand alone generators, supplementing power production with their engines which are easily capable of providing electric current to the gird.

Plug-in hybrids are becoming increasingly popular. Cars like the Chevy Volt operate on a “dual fuel” basis. They can run on gasoline stored in a tank or on electricity stored in a battery. Such vehicles, when connected would provide power to or take power from the grid as needed. Pricing would be computer controlled to pay a premium to power providers at peak demand times and charge appropriately for electricity delivered to vehicle owneers as needed.

Although the idea for V2G was originally planned as a method of covering the need for peak demand in urban areas, the same idea could be used to smooth production system wide. It could be an elegant way to compensate for the intermittency of sustainable energy supplies such as wind and solar.

Electric companies of the future may not be the massive monolithic power providers of today, but rather simply brokers for grid distribution of a diffuse set of suppliers. Large wind turbines, small solar arrays and even the family car parked in the garage, all contributing through a computer managed network.

“The future belongs to those who believe in the beauty of their dreams.” ― Eleanor Roosevelt