Fin MacDonald

Information on me and my current projects

Tag Archives: solar

EEBE Walkthrough Audit

Today our groups performed our walkthrough audits for the Energy Efficiency and the Built Environment project. Our house that we audited was only a couple years old and was quite energy efficient already. We were armed with some pretty sophisticated tools and a great set of checklists that we prepared.

Dan Boyd from the Nova Scotia Homebuilders Association was on hand to perform the blower door test for us. The home we audited previously tested at 1.4 air changes per hour (ACH) but we won’t know how it faired out today until we get the data entered into HOT2000.

We tested the envelope of the building with the thermal imaging gun to look for thermal bridges. We found lots at the studs in the walls and the ceiling, as well as all along the headers and rim joists. Thermal bridges are pathways where heat escapes and are common in standard construction. Modern construction methods are working to eliminate them all together but not all builders are using them right now. We didn’t find any missing insulation or sagging around the windows.

We used an air quality meter to measure temperature, humidity, and CO2 levels on each floor. This will help us determine how effective the ventilation system is. The home has a heat recovery ventilator to reclaim the heat during the ventilation process.

The lighting was quite different throughout the house. We found compact fluorescent (CFL), halogen, as well as incandescent bulbs depending on what fixture we were looking at. We will recommend that the incandescent bulbs be replaced with CFLs.

South is located to the rear of the home and there is an excellent solar resource there. We will be creating a model for a solar system to determine the payback before we make that recommendation. I expect it will be feasible because of the location and the number of occupants (the more people the more hot water used). We will also look into using a drain water heat recovery system to reclaim heat from the drain water.

Water efficiency on the inside of the house was given attention when the home was designed, but the exterior could have some improvements. There are a lot of plants outside so a rain barrel to capture rainwater for watering would reduce potable water usage. Mulch should also be added around the shrubs to reduce evaporation from the soil and hopefully reduce the need for additional watering.

The heating system is about as good as it can get. The owner has an air source heat pump with an electric furnace for a backup. Since the subdivision was blasted out of the side of a rock mountain a ground source heat pump would be too much of an expense to be worth it.

Tomorrow we will start to sift through all the data we collected and come up with some more ideas for low cost or no cost recommendations for the home owner.

Solar Pathfinder vs Solmetric iPV

Today I conducted a little test to compare the performance of two low cost solar site assessment tools. I consider low cost to be anything under $1,000. These tools provide infomation about the amount of available sunlight that falls on a surface. They do this by examining the landscape features in the area that provide shade at different parts of the day such as buildings and trees. These tools provide a percentage of available solar radiation you can expect to receive. This can then be combined with weather data and solar panel information to perform preliminary energy calculations using energy modelling software. This site assessment information is supplied for each month however for the purpose of this test I am only going to compare the total annual values.

The two tools I compared are:

1) Solar Pathfinder (http://www.solarpathfinder.com) $299 + $199 software

Solar pathfinder image. The black areas inside the ring mark the obstructions in the surrounding area. This image is traced using computer software.

2) Solmetric iPV iPhone application (http://www.solmetric.com/solmetricipv.html) $29.99

The Solmetric app lets you trace the obstructions directly with the iphone.

The calculations for the percentage of available sunlight were as follows:

Solar Pathfinder: 84%
Solmetric iPV: 86%

Both of these tools require tracing so they have a element of human error involved. When using the pathfinder you take a picture of the equipment and trace it using the computer software. When using the Solmetric app you trace the horizon directly with the iphone. Given the close proximity of the results I don’t really feel as though one is any better than the other from a performance standpoint. When you consider the price the Solmetric iPV iPhone application is the clear winner, but only if you already own an iPhone.

Solmetric also makes professional site assessment tools in the $2,000 price range that do not require any manual tracing and are remarkably accurate.

Web Energy Logger installation today

Today I installed a web energy logger on a solar thermal system in Halifax. The system is in a large multi-floor residential building. The entire process took about 3 hours, which is a new record for me. The solar data logging system installed has 5 temperature sensors and a current switch to detect if the pump is on. With this setup we are able to calculate the amount of energy that the solar panels are able to extract from the sun and supply to the glycol. The data logger will provide real time data once each minute as well as log the data to a .csv file for analysis at a later time. It connects to the WEL Server (www.welserver.com) to transmit the data over the internet.

The limitation of this data logging system configuration is that it is unable to calculate how much of that energy is actually transferred to the water. Since the solar system was already installed prior to the decision to add a data logger, it does not have electronic pulse flow meters. Flow meters connected to the data logger would allow for accurate calculations of the energy supplied to residents and the savings on the buildings power bill associated with that energy. The decision to go back and install pulse flow meters will rest with the building owner.

The Web Energy Logger (WEL)

The WEL is a low cost but effective data logger that can be used to monitor energy use or generation. It contains a one wire bus that allows digital sensors to be strung along like christmas tree lights. It also contains 6 pulse inputs, 8 run inputs, and 2 4-20 mA analog inputs. Pulse sensors return an electronic pulse signal and applications may include paddlewheel flow meters for water flow. The digital pulses can be counted and converted into a volume flow rate. Run sensors tell you if the device connected is on or not. Current switches can be installed over power cables to current and return an on/off signal. 4-20 mA sensors send a mA current signal that can be scaled into engineering units.

Inside the WEL you are allowed 150 variables. These can be sensor inputs, constants, or simple expressions of other variables. The WEL has limited internal memory so it is limited to simple 2 variable expressions and is not capable of doing exponents or square roots. That being said most energy calculations can still be performed inside the WEL. It also has support built in to maintain running totals for the day, month, or year of any variable.

The WEL uses a rabbit board network chip to connect to the internet and transmit the data. It can be set to log data at any frequency, entered in minutes. By default it connects to the WELserver (http://www.welserver.com). This webpage contains a map of the world with all the other WEL’s shown on it. It is a great tool because it allows you to not only monitor your system, but see how others are doing as well. With some ingenuity you can connect the WEL to your own server to record and present the data there. The WEL posts data that can be received by a simple CGI or PHP script.

Typical WEL applications include monitoring of geothermal, solar thermal, solar photovoltaic, and energy use. The WEL is diverse enough to be used in other applications as well. A device called the WattNode (http://www.ccontrolsys.com/w/Advanced_Pulse_WattNode) must be added if you want to measure alternating current.