In the past month my friend David Brenner and I have made a great deal of progress with the wind turbine remote Arduino power meter.  The idea behind the project is to log the amount of power generated from the wind turbine and have the data automatically be uploaded online where it can graphed.  There are similar products on the market, but they are designed for much larger turbine and solar arrays, and thus are expensive.  We wanted to utilize the Arduino micro-controller as it versatile and inexpensive.  With all the parts the costs is around $80, which is a fraction of the cost of other solutions.

The power meter works by reading the current flowing from the turbine.  We are using a Hall Effect current sensor as it is very efficient and can handle up 30 Amps.  Based on the amount of current, the sensor outputs a voltage which can then be read by the Arduino’s analog to digital input.  An issue with the Arduino’s ADC is that it is limited to only 1024 values ranging from 0-5 volts.  This means that the Arduino is not very accurate and can only sense a 4.8mV change.  The issue we had was that the current sensor’s output voltage changes by a very small amount and the change couldn’t be read by the Arduino.  To correct this, we fed the current sensor into an amplifier stage to increase the output voltage so the Arduino could read smaller current changes.  The current sensor outputs 1.5v with no current, so to ensure that we weren’t amplifying the voltage when there was no current we needed to implement a 1.5v offset.

The Arduino microcontroller reads the data from the ADC input and then sends the data through the Internet to a server.  We are utilizing the wireless repeater portion of the wind turbine to transport the data through the Internet.  The server then reads the data and stores it in a mysql data base so graphs can be created.  The Arduino sends a new power reading every one second, so the graphs can be extremely accurate if we wish.  The remote power meter is currently in field trials to ensure the basic functionally works correctly.

The Purist solar hot water pump and controller has some cool software which logs and graphs the performance of the system. Below is a graph of the performance of the solar thermal system during the day. This information is for the pre-heat tank which then feeds a smaller hot water heater. The pre-heat tank uses solar panels to heat the water from the street which ranges from 40-55F to a much warmer temperature. This allows the water heater to use vastly less energy since it doesn’t have to heat the water as much. On a day like this, the water heater wouldn’t even turn on since the inlet temperature is warmer than the 115F set for the water heater.

The yellow line is the temperate of the water at the top of the tank, the blue line is the temperature of the water at the bottom of the tank, and the red line is the temperature of the solar panels on the roof. During the morning two showers are run, which causes cold water to enter the bottom of the tank. At about 9AM, the solar kicks on and it slowly heats the water until 3PM.

A solar hot water system was recently installed at my family’s house. The government incentives which accounts for about 30% of the system and the fact that the old hot water heater was broken were the main drivers of the project. The system is designed to provide hot water for four to six individuals which equates to 75 square feet of solar panels on the roof. We are using a dual tank solution since this is more efficient, but more expensive than just using a single tank. With the dual tank solution, one tank acts as a preheat tank which preheats the cold water from the street while the other tank is the hot water tank which keeps the water at a constant 120F. Since the water from the street is between 40-60F, a great deal of energy is required to heat this to 120F. n With the preheat tank, the solar panels heat the water from the street before it enters the hot water tank so less energy is needed to heat the water to 120F. The hot water tank has two backup sources in case the preheat tank is feeding water colder than 120F. During the winter the backup is a tankless coil in the boiler and during the summer it is electric which allows the boiler to be turned off.

We have only had a couple days of sun and the rest has been snowstorms. On a 30F sunny day, the preheat tank started at 58F in the morning and at the end of the day was 82F which isn’t bad considering it is 105 gallons (double the size of an average tank). The glycol (water freezes) which flows through the panels was a constant 140F which is incredible if you think of the low UV radiation that the sun produces during the winter months. Hopefully there will be a couple sunny days in a row to get the big preheat tank over 100F.

There are two types of solar energy, photovoltaic’s which produce electricity and solar thermal which produces heat. Photovoltaic’s gets all the attention as electricity is the universal power medium and cheap photovoltaic’s could revolutionize the world. While photovoltaic’s are still rapidly developing since its invention over 50 years ago by Bell Laboratories solar thermal has been a developed and proven technology for many years. Solar thermal uses the sun’s energy to heat a liquid. It is the same concept as placing a garden hose in the sun for an hour: the water will become hot. There isn’t much technology can do to improve heating a liquid so most of the solar thermal technology from the 1980’s is the same as today. There has been one new additional technology which is evacuated tube solar panels. Evacuated tubes are slightly more efficient than the older flat plates panels and work better in cloudy and colder climates. The downside is that they are costlier and to some people not as pleasing on the eyes. Since solar thermal is a mature technology the prices are very reasonable and the payback is just a matter of years compared to 10+ for most photovoltaic installations.

Over the next week I will be updating the site with information regarding the solar thermal installation installed at my family’s house.

There is an interesting article on Nanosolar’s blog regarding municipal solar power plants. If you never heard of Nanosolar, they are a new solar startup that claims it can produce solar panels at a fraction of the current cost. Their first factory is online and they have an impressive list of investors. If their claims are correct they will revolutionize the solar and power industry. The articles discusses how municipalities could create there own power plants user solar. Using renewable energy to power municipalities isn’t a new concept and clearly demonstrated in Hull, MA where a pair of wind turbines power over 10% of the town. Municipalities have used wind power instead of solar due to the much higher cost of solar power, but wind power is only economical in limited geographical areas. Solar works well in many more locations and the approval process for a field of solar panels is much easier than installing a 300ft tall wind turbine. If power plants owners have to start paying carbon taxes and if solar can become less expensive, then solar power plants could become a reality in the near future.