When planning a solar PV system there are free tools and apps that will help understand how to select your new PV system and how to maintain your existing Solar PV system.
Tools and Software
View Existing Solar PV Outputs-The free software provided by SolarEdge (a solar company) is very good . They allow customers to share how their solar PV system is performing in different parts of the world. One only needs to type in a location and if there are any installations near you they will show up. The SolarEdge link is here. Search for county locations rather than the town name.
European Union (Photovoltaic Geographical Information System)
This tool allows one to see the expected yield of a PV system in different countries. One selects a location on the map first and then enters the details of your system or planned system. Previous weather data is used to model the results. If one uses the daily data option one can evaluate what would happen if one angled the Solar panel slope and the expected solar pv yield with the changes. One can keep the same setup for your site and pick different countries to see the changes.
The below image shows the steps to get you started ie 1,2, 3,4,5
View the movement of the sun around your home or select your solar PV location.
This software will allow you to view the solar changes of the sun as it moves around your home or solar PV system over time. The app is called Sun Surveyor Lite. It is available in a free version or a paid version on both android and apple platforms. The free version works well.
When calculating the slope of one’s roof the Bubble Level app is useful.
Check if your PV System is working correctly .
When one has a solar PV system -faults can occur. Some of these faults will not show on your solar PV app. Most PV systems installed do not have individual PV panel management unless one requested optimisers or microinverters. What is required is a tool to check if your PV system is working efficiently and generating the correct output power.
When a solar PV system is installed the installer will usually carry out this test before completing the installation. This test ensures that the designed output power (in watts) matches the solar PV input power (w/m2).
The first tool one needs is a pyranometer or also known as a solar irradiance meter or solar radiation meter. It measures the light that generates electricity within the solar panels-this is the approximately the wavelength from 300 to 1200 nanometers below.
This solar irradiance meter is calibrated in watts per m2 (w/m2). The light that one can see with ones eyes is between 400 and 700 nanometers. This means that solar panels can convert more light into energy than what the human eye can see. The majority of the heat one feels on your skin is the energy above 700nm and the solar panel can use this light/energy.
As mentioned before there are in principle 3 types of silicon used to make solar panels -mono crystaline, poly crystaline and CIS. Below is a side by side comparison of how the types of silicon use light energy shown from the above image.
If a solar panel is 20 % efficient at converting this light into electricity then the majority of the other energy ends up as heat. As stated before an increase in temperature negatively affects the output power of a solar panel. If one uses the online calculator app below and adjusts the temperature one can see the effect temperature has on the solar panel.
Convert Solar Irradiance (W/m2) into power (Watts)
When one has a solar pyranometer/irradiance meter it provides the data for the App.
This software converts the solar irradiance measurements (w/m2 -watts per meter square) into electric power (watts or kw/h). One can enter the size of your solar panel and the number of solar panels and the output power is calculated in watts) . Solar PV Irradiance converter.
Cleaning/Maintaining Your Solar Panels.
There is a correct way to clean solar PV panels and there are risks. Below are the recommendations by the manufacturer Q CELLS. In summary-
Solar PV Cleaning
Do Not use a hose with water
Do Not clean modules with water if there is a risk of frost
Only clean the modules when they have cooled down
Use kitchen roll for stubborn dirt and not fleece or cotton cloths.
PV Panel Options-Output wattage of pv panels are typically available in the range 270 Watt, 340 Watt, 375 Watt, 455 Watt. A manufacturer’s brand name will add to the price. Some brands names are LG, QCELL, LONGI, REC etc. A manufacturer warranty can be up to 25 years. A performance warranty of up to 25 years is available.
Example -A Qcell 340 W , 25 year manufacturer warranty and performance warranty can be purchased for €60 ex vat, a REC 365W for €165, a LG 440W for €261. Some manufacturers are now including a labour warranty of between 10 and 25 years.
Inverters Options-The standalone single inverter price varies from around €160 for a 1.5kw system and increases to approximately €1,300 for a 10kw inverter for the domestic market (single phase). The number of MPPT channels provided in the inverter changes the price-a single MPPT channel inverter will usually be cheaper than a dual MPPT channel inverter. MPPT methods also affect the price (a list of the mppt types available are listed here–for the techies.) As above the manufacturer brand name and the length of the manufacturers warranty also dictate the price you pay.
Hybrid Inverters (those that charge batteries) start at around €600 for a 3kw system and increase to €1600 for a 5kw system. The warranty varies from about 2 years to 25 years. When purchasing an inverter one must ensure that it has a certificate of compliance to match the national grid profile (a grid profile determines when the inverter should switch off and on if there was a power failure) . So purchasing a cheaper inverter online might not be compatible with the national standards required in each country. This grid profile is usually programmed/selected when installing the inverter.
Another option when purchasing a central inverter is to install optimizers . These provide as a means to improve the solar output if shading exists when using a central inverter. These cost around €50 each.
Microinverters prices start at around €100 for a 350 watt pv panel and increase to approximately €160. Warranty’s vary from 10 years to 25 years. Some brand names that exist are Enphase, TSUN , BPE. They require a single management control unit that controls, configures and allows one to monitor the performance remotely on a desktop or mobile phone App. The brand name also carries a cost. The microinverter is able to monitor the performance of each individual solar panel and inform you about an individual failure or issues. They also offer one of the best ways to manage shading from trees, chimneys, etc., or different orientations as stated earlier. This single control unit costs approximately €140 to €280 depending on the functions you require. These unit types generally have an AC charging function similar to the Tesla battery systems.
When the sun is close to the horizon Solar PV Panels generate less energy than when the sun is directly over the Solar Panel.
The reason for this is that the sun’s rays pass through more of the atmosphere thus reducing the sun’s energy (photon energy) on the PV panel. If it is an overcast day they will produce less energy. To translate this into numbers- in the winter when the sun is low in the sky (say 14 degrees from the horizon ) the total irradiance from the sun measures around 780 W/m2 (watts per meter square) with a clear sky. In the summer one would expect to see 1100 W/m2 (55 degrees from the horizon). The bottom line is that if one can point the solar panels perpendicular to the sun one will get a higher electrical output kw/h.
In order for consumers to purchase and compare solar PV panels manufacturers have agreed a way to compare the output power of Solar PV panels and this test is referred to as Standard Test Conditions (STC) . The test is done at an irradiance of 1000w/m2, at a air mass of 1.5 (approximately 42 degrees from the horizon) and at a temperature of 25 degrees. The value w/m2 is how solar irradiance is measured while the PV panel output power is measured in watts. The following calculator will help you understand how the output power of your PV System (in watts) is affected by solar irradiance and other factors. Check your Solar PV Output Power in watts.
Most roofs have a pitch of around 35 degrees. The best direction to point the solar panels is usually south but with some solar PV installations, it is possible to have some pointing South and others pointing West in order to collect as much energy as possible during the summer. Meters used to measure solar irradiance are called pyranometers, Solar irradiance meters, or solar radiation meters. An example of how these meters are used to locate, measure, and check if your Solar PV system is working efficiently is shown below. The calculator above can be used with these meters.
PV Panel Shading
A factor that has a significant impact on the output power of a PV System is shading on an individual Solar PV panel. This can take the form of chimneys, trees or other houses. The reason for this is that if one examines each solar panel one will see that it is made up of individual cells wired together in series to make up a full solar panel (see below). If one or more cells are shaded when installing a traditional solar PV system (One inverter) the output power is reduced for the whole system. There are other solar PV systems that use microinverter’s or DC optimizers that will not be seriously impacted by shading thus the consumer will generate more electricity.
Another factor that significantly reduces the solar panel output power generated is the panel temperature. We are lucky in Ireland to have a mild climate with day temperatures not usually going above 20 degrees (on a good day). What this means from a practical perspective is that a solar panel in Ireland will generate more power than a solar panel in Spain on a cloudless day.
Solar PV Components.
The components that typically make up a solar PV system are PV rails which support the PV panel , roof brackets/hooks that connect the rail to the standard tile or slate roof and clamps that connect directly to a specified roof types such as zinc or steel roofs. There are separate pv panel mounting systems for flat roofs or ground mounting. If one wants to explore PV mounting system suppliers -use a google search for “roof mounting systems for solar panels“. As I used a zinc roof one must ensure expansion joints are installed in the pv rail every 3 meters.
PV Panel Types
There are three types of PV panel cells -monocrystalline (these aesthetically have an even black finish –shown above), Polycrystalline which have an uneven shade of blue crystal cells and CIS types. Monocrystalline are more common and are slightly more expensive than polycrystalline and CIS are now more difficult to purchase (shown in part 1 of the blog). The options available when selecting PV panels other than the type above are length of equipment warranty and length of manufactures performance warranty. The majority of PV panels generate DC (direct current). All PV panels must be angled at least 3 degrees from the horizontal. PV panels produce DC power and to give you an idea of what 4 panels can produce and the energy they can generate for a load, loose connections or cable damage please see this video .
Inverters are principally available in 3 types -one central inverter for a full PV installation without battery charging, a central inverter that has inbuilt battery charging facility and micro inverters for individual panels or a pair of PV panels.
Central inverters. The important factor here is the warranty length and how many MPPT (maximum power point tracking) channels does the inverter have. If one was installing 8 panels in two rows (strings), two separate MPPT channels would mean that the two rows of 4 panels would have their own ability to generate power independently of the other row (string) so for example if one row of pv panels got dirtier/shaded or a fault occurred on one panel the other row would keep generating at full power. As all PV panels are not exactly the same the separate MPPT channels allow for a higher output yield . When selecting an inverter one must match the PV Panels to a particular Inverter. Once this is done adding more panels can become restrictive and may mean that one needs to change the inverter again. If the inverter fails the whole system fails. If one needs to change a PV panel in the future the central inverter may also need to be changed.
Micro Inverters-simplify the installation of a PV system and permit simple expansion. It is really close to plug and play . Because they are paired with a PV panel they manage shading better than a central inverter. The voltage generated is also different to the central inverter in that it produces low voltage AC -the same voltage as all domestic appliances like fridges, washing machines etc. There is also less of a chance of fires because of loose connections/damaged cables. They offer full management of your PV system with apps and individual panel performance monitoring. Pv panels must also be matched with the individual inverter using the PV panel data sheet. This is one such calculator.
As stated before I personally am not in favour of using batteries for PV panel installations. The reason is that batteries are expensive, they are another failure point and I feel they are needed for vehicles more than PV installations. For example, a 300 litre water tank can store 20kw of energy at 60 degrees (a stainless steel water tank would cost around €1000-while a similar battery could cost €10,000 to €15,000 and still would need to be replaced after approximately 6000 cycles). All homes need hot water thus sending any excess electricity from the PV panels could be fed to a hot water tank. So instead of adding batteries why not consider changing the hot water tank and place elements at the bottom of the tank and the middle of the tank.
Another good idea is to switch to night time electricity which currently is half the price of the day unit to supplement the lack of PV power during the winter to heat the water tank.
My preference is to install a side arm heat exchangerto the water tank so that I can achieve better hot water stratification. Stratification is the creation of layers of hot water free from movement/mixing when one heats water. What happens for example is when cold water enters the tank at the bottom it can mix the stratified layers of hot water thus reducing the water temperature. It is difficult in Ireland to purchase water storage tanks that have simple devices fitted that maximise stratification with devices such as an inlet baffle on the cold water inlet .
To complement the above use of a water tank one can add a single shower pump and feed all showers from the tank.
The above will reduce the use of electric showers which are the highest electrical energy consumption devices in a home. From personal experience, I can say that 150 litres of hot water (half a 300 litre tank) can provide 6 showers a day. Currently, I use off-peak electricity to heat half the tank.
If you are a new build one can plan to install the shower pump outside the house in an insulated chamber below ground level near the tank. This is what I have done to reduce the noise as we have a single-story home.
As energy prices increase and the switch from fossil fuels takes place one is left with few options to offset rising electricity costs. In this blog I am going to go through the choices that are available when using Solar PV. Solar PV systems typically generate DC (direct current) power and this is then converted to AC (alternating current) power for use around the home. These systems also synchronise with your own electricity supply grid so that you can use it. The standard system one purchases will automatically disconnect from the national grid if there is a power failure thus ensuring that you do not send power into the national grid. The abbreviation PV stands for Photovoltaics (when light is used to generate electricity from a semiconductor material).
A common-sense starting point before considering Solar PV is to try and reduce your existing electric energy use. This might be as simple as changing old fridges, washing machines, dryers, or pumps. If one uses electricity to heat one’s house then insulating the house and upgrading the hot water tank is also a good starting point. For example, one 300 litre water tank will store 20kw of energy at 60 degrees Celcius (see the previous blog on the water tank). Typical battery systems can not economically or environmentally compete with water as an energy storage system. All homes need hot water and you will not find a safer, more economical, and environmental approach for storing excess energy from Solar PV. One can also opt for reduced price electricity at night (approximately half the price of daytime electricity) which helps the national grid balance its load.
A simple starting point is to visit your home supply meter and work out how much electricity you use per minute on a typical day. This is the load one uses without using main appliances such as kettles, cookers, water heaters, etc. It typically would include fridges, ovens timers, clocks, computers plugged in, modems, etc.
To do this one only needs to look at your meter and it will display a number that tells you how many revolutions or pulses it uses to record one Kw/h (kilowatt per hour) of electricity. One is billed by your electricity supplier for each kw/h you use. Above and below are examples of where you can find the numbers. In the example above the digital meter has 1000 Impules per kw/h and the old type shown below has revolutions -in this case, it is 250 revolutions per kw/h.
To calculate your typical energy use without using main electrical appliances follow this example. Set your phone/ watch to the stopwatch setting. When you see the first pulse start your timer and visually count the impulses in that minute. If you get 10 impulses in 1 minute then multiply 10×60 minutes=600 impulses in an hour. So we know that we now use 600 watts of power in one hour without using main appliances.
In the old type meter, you will notice that there is a red/black mark on the wheel when it revolves in one revolution. In the meter above we can see that it does 250 revolutions in one hour to record 1kw/h use of electricity. So if it does 125 revolutions it is 500 watts of power in one hour or 0.5kw/h. One can use the same principle above and use a two-minute count to increase the accuracy of your calculation. InPart 2 I will look at what PV systems are available to purchase and the parts that make up a good Solar PV system.
There are many options today when deciding to build. One can use a factory built design or use traditional block work or timber frame on site. Some factory built designs are as follows by way of example http://www.scanhome.ie . One can select the level of input oneself such as only construct the frame and say the self builder can do the rest or let the builder/supplier do everything.
How much Work does a self builder take on.
As a self builder I would try and get the foundation, frame, roof and windows installed then one can work in the dry to finish it. One is left with indoor wall completion, plastering , air tightness, Heat recovery, Wiring, Plumbing, Rain Water Harvesting, House heating System, Water heating system, floor finish, Painting, furniture , kitchen more than enough work for the self builder. The above need to be well thought out before laying the foundation or erecting the frame and the finish design of the roof.
The Building Standards-Self Build
One needs to comply with the building regulations. Always remember these are the minimum standard. It is always better to go for a home that will last well into the future that is warm and supplies fresh air. A lot of new homes built today are of a poor standard and this can be seen in the UK and Ireland. See example https://energysaveguy.tumblr.com.
The Sales Pitch
There are buildings that can receive different rating systems such as LEED and BREEAM. A good video on the good, the bad and the ugly of these can be seen here. They focus on equipment and energy accessories so it is best to leave these and focus on the basics. What are the basics –Insulation, Air-tightness, Windows, Heat Recovery (fresh air supply), and minimising thermal bridging(heat loss through details on the build). When one does the above one finds that the heating system is simple, the house costs very little to run and is healthy if the correct materials are selected and installed in correct sequence during the build.
The Gold Standard-Passive House
The highest energy standard to build a house , an apartment, school or commercial buildings is the passive house standard. It focuses on the basics and uses physics rather than rating systems to design the building. All the calculations are done before the house is built on a passive house planning software package (PHPP) which takes into account for example how much solar heat the glass in the window will leave into the house, how much heat will be lost through the glass from the inside to outside, how much heat is lost through the frame, and the heat lost on how the window is installed in the wall. Every building detail physics are analysised to ensure that one ends up with a comfortable home.
The plan is to have all the outdoor lighting (Using LED -Light Emitting Diodes) operate from a 12 volt recycled car battery and recharged by a solar PV panel. The lights will be controlled by the in-built timer in the MPPT charger. This will keep the cable cost to a minimum (small cable size) and keep the voltage low enough to be safe in a garden environment (when digging and planting).
Below is the CIS thin-film solar PV Panel (copper indium gallium selenide ) I mounted on the shed roof.
I selected a 60 watt solar PV panel that was manufactured using CIS . This type of panel has a higher output voltage of 52 volts which work better with the charger I selected rather than the typical mono or poly crystalline cells of 30 volts . One needs to select a charger to suit the PV one buys. The panel was mounted on a 3 degree pitch facing south (see above) . During tests I found that this type of cell is more forgiving for shading and dirt (bird droppings mainly)-it maintains a consistent output power . For example when I partially shaded it with my hand it still outputs almost the same power. If one partially shades a monocrystiline /polycrystaline cell it will cause it to stop working as all the cells in the unit are wired in series.
Measuring the efficiency of the installation.
In order to check the efficiency I mounted a pyranometer at the same angle (top left of image) so that I could ensure that connections and charger were working correctly. One needs to know the input power in order to check the charger efficiency and that the system is working correctly.
The MPPT Battery Charger
After reviewing products available I opted for the Victron SmartSolarCharger MPPT 75/15. This can charge a 12v or 24v battery system. When selecting a unit one needs an inbuilt MPPT which stands for Maximum Power Point Tracker. In Ireland and the UK this is important because of our natural cloudy weather which causes the solar panels to vary their output as the irradiance changes . What happens is that the solar panel’s internal resistance changes when the irradiance changes (sun shining on panel) -so the job of the MPPT charger is to change its load resistance as the solar panel’s internal resistance changes. When the load resistance matches the solar panel resistance then the maximum energy can be transferred to the load. If a charger did not have the MPPT then the efficiency of the complete system would be compromised. While there are different methods (algorithms) used to build MPPT units some are more efficient than others. Some of the different MPPT design options available are called perturb and observe , Incremental Conductance , short circuit current method etc., The idea of all these MPPT systems is to get the maximum power from the solar panel -some MPPT are low cost and others are more efficient in cloudy weather.
There are a number of advantages of the unit compared to others that I researched . It has charging algorithms for different battery types such as deep cycle and lithium ion. It has a bluetooth connection so that one can programme and monitor the output without other devices /connections being required. Another advantage is that it has a lighting timer that can automatically switch lights on and off at night or at dawn.
Some of the advertised benefits of the Victron MPPT unit are:
The Setup .
The setup is as follows . I plan to move the battery out of the shed as it is not best practise to have any battery system in a shed/garage/house because of the fire risk. The charger is mounted on a fire resistant material (Magnesium Board)
In order to access the data collected one logs on using the Bluetooth connection on your phone/tablet and the data is available. Below are different samples of the data available . The first indicates the solar power collected and the load usage. If the battery is fully charged it will take little or no power. If there is a load during the sunshine hours then the battery and solar panel will supply it.
Below is a chart showing how the MPPT charger adjusts its output/load to follow the changes in the irradiance levels (power from the sun) per second .
As I am able to measure the input power using a pyranometer I built I was able to see that the system was working efficiently. The data below is the output power from the charge controller when the input power from the sun was 471 watts/m2. The CIS panel provides 60 watts output when the irradiance is 1000 watts/m2 at STD (Standard Test Conditions) . This would mean that if the input power was 500 watts/m2 then the output would be 30 watts/m2. The data from the charge controller indicates an output power of approximately 27 w/m2 for the 471 watt/m2 input power.
Self-Build for Water Leaks, Power Measurement and Temperature.
The task of monitoring for water leaks, temperature and measuring power is best served by some remote tools available on the market.
Most tools rely on Wi-Fi, zigbee, 433mHz etc., signals to communicate through the internet connection remotely to your phone.
This in itself is a weakness as if your wi-fi is not working then most of these tools fail. But if the wi-fi or ethernet connection does not fail then these tools are of value.
Lets look at some of these tools that I feel are worth considering.
The lowest cost unit is the Sonoff suite of products. The list is comprehensive and the cost is low. For example the wi-fi / 433Mhz central hub for these devices costs less than €9.00 and as an example the water leak sensors are approximately €8 each and it uses a lithium battery for reliability (needs to be purchased separately).
The product is very well made and a certain level of IT skill is involved in setting these up. It operates at a very safe radio frequency like that of your car remote control rather than higher frequency’s but the hub uses wifi so if one keeps it close to your router and keep the router as faraway as possible from you it is probably the best approach.
I would advise that a separate sensor unit (regardless of which product you select) is installed in a location that you can easily check to ensure that the system is functioning correctly as water leak sensors can end up in locations that are difficult to inspect and check such as behind dishwashers etc. One needs to change the battery every year or two on each of the sensors or when your test unit fails.
Type in smarthings hub in the search of their web site and one should find the relevant devices . Check your own country samsung web site for compatibility.
Another company that provides value is Shelly. They supply multiple sensor types including water leak sensors that integrate with the power unit below.
I have not purchased this unit but it looks like good value at €69 but it uses wifi. It is made by Shelly https://shelly.cloud/
A unit that measure power consumption and provides a Bluetooth option also looks like good value. It is the AT3010 AC50~320V 100A 3KKW Phone App AC Meter. It costs around €15 and can be purchased from https://www.banggood.com . It will need an enclosure to house the unit and it does not use wifi which is a benefit. I purchased this unit as a test and I am about to set it up. I will use this meter to monitor the cost of heating the house and also monitor the condition of each storage heater.
I am just getting around to installing the light switches . This is how the finished light switches look at the moment. Later on I plan to change the front plate of this switch to one of the other options such as glass, wood or marble.
This is what the above light switch looked like before installation. Standard switches can be used if one uses the method described below. I used a screened alarm cable to connect the KNX binary device known as a universal interface. This voltage is extra low around 3 volts DC.
As seen above this is what a typical KNX lighting distribution board looks like. One has a Power Supply (top left) and a programming Interface (next to power supply) . The three actuators (12 way) on separate rows send power directly to the rooms or other devices such as towel heaters. Functionality such as timers, last state before power failure, purging (automatically switching on pumps/valves to ensure they do not stall) etc is already built into the KNX technology.
This is one type of LED Driver I have used to power each LED. Typically when one buys an LED they have already tried to fit all the electronics contained in the above unit in the lamp one buys . This is one reason why led lamps do not always live up to their expected life time of 50,000 hours. The majority of LED failures are due to heat stress. I am using 9 watt LED in the housings shown above and the Power supply is a separate unit. For lower power LEDs one requires less electronics.
Floor laying continues with the Junckers System. The floor boards are 22 mm solid wood with a proprietary clip system. Each of the metal clips (shown below) connect each floor board. The clip type one selects depends on the expected humidity levels in the home. I used a soundproof underlay on the concrete floor. One can also nail this type of flooring.
Skirting Board Lighting
I started the design of the skirting board lighting that will be powered from a DC source (battery) connected to a solar panel. The idea is that this lighting would be on when it is dark and would also act as a lighting system if there was a power failure in order to minimise the use of candles.
The light output of this lighting would be equivalent to a candle and they are placed in bathrooms and corridors in order to allow one to walk around the house at night without switching on the main lights.
A first fix of how they will look is as shown below.
Different HRV units have different mounting options. Some are floor only, wall only or ceiling or all three. Some units like the Airflow DV145 that I purchased can be mounted on the floor or wall while smaller Airflow units can be mounted on the ceiling, floor or wall. One needs to make sure that there is space underneath for the condensing water outlet. If the unit is mounted on a wall make sure that vibrations do not interfere with noise sensitive rooms such as bedrooms. I mounted ours on a sound proof and isolated base and used other sound proof methods to isolate it from an adjacent room.
In the early stages of the build the fresh air inlet and stale air duct positions were selected with a spacing of over 2 metres. If the supply and exhaust ducts are too close this can interfere with the correct operation of the HRV unit. This entailed finding an HRV unit that would be flexible in the options available to simplify the space required for the main ducts and keep the runs as short as possible. The lengths of the supply and exhaust ducts play a big factor in the efficiency of the whole system. The Airflow unit comes in a right hand and left hand model. I found that different manufacturers have different duct layouts even though they have Right Hand and Left Hand models.
DATA from the HRV with the Post Heater On
One can see from the above graph that with the winter sun I needed to switch off the heater and switch to summer bypass as the weather improved. The next plan is to automate the bypass mode when the solar irradiance level measured in W/m2 and temperature exceed a set value then the HRV would automatically switch over to the summer bypass mode as one is gaining solar heat.Update-2022-We found it easier and more economical to switch of the post heater permanently and set a base heating load of 1.35kw (200m house floor area) for the winter and manually switch on a 600 watt electric oil heater for days or evenings when the solar gain did not happen. In this way there will be days when one is not in the house and it is proving to be effective also. Also as the house id energy efficient the room heats up quickly.
As the internal fans are to the rear of the unit I added a small amount of soundproofing as an experiment. I was able to reduce the db level from 49 db to 44 db. Each 3 db approximately equates to twice as loud or twice as quite depending on whether you are increasing or decreasing the level.
I mounted the unit in the hallway entrance so extra sound proofing was required. If one has a utility room then extra sound proofing would not be necessary I feel.
Following on from the previous blog I had a display panel built that calculates the HRV efficiency using the supply method and extract method by means of the Modbus data connection available in the HRV unit . In the Image below one can see S100 (Supply method for calculating efficiency) and the E 90 (Extract method ) as a percentage. The supply method is the one typically used by manufacturers in brochures. The D displays the difference .
The top line displays the temperatures of the Inside air and the air leaving the house followed by the Outside air temperature and the supply air temperature to the house. When the post heater is on the efficiency calculated with the supply method sometimes displays a number greater than 100% as the heater is built into the unit and mounted before the thermostat. The extract method for calculating the efficiency is a closer representation of the real efficiency and it is similar to the passive house method (uses the same principle ). The extract method does not use the supply air temperature in the formulae.
Access for repair and maintenance.
Some HRV units require side panel access so ensure that you have enough space to get access to fans/ filters for cleaning and maintenance . The Airflow DV145 can be fully maintained from the front cover so it can be fitted in a corner space without restricting future access to internal parts. The filters are also maintained from the front panel.
Functions and Benefits
When selecting a unit- what was important to me that there was an integrated summer bypass function in the unit, software control by a smartphone with data capture (a manual control panel-is an extra cost and another item that could fail) and an integrated post electric heater. Airflow also sell a ground source heat pump option connection to the HRV which I did not purchase. For those installing a stove / fireplace one requires a Fireplace function built into the HRV . The Airflow DV145 has this function.
September 2018 performance.
The summer bypass function allows one to bypass the heat recovery function during warm weather or reduce winter sun peaks (when the sun is low on the horizon). The way this works is to bring the air outside directly through the ducts in order to reduce the internal temperature at night or during the day. One can see from the image above on the 28 and 29th of September I forced the HRV unit to summer bypass during the day to keep the temperate under control with the winter sun. No heating had been switched on for the month of September and the night temperature outside has hit the lowest in the same month of 2 degrees.
The Airflow unit is software controlled by means of your phone or your personal computer . This helps keep the HRV cost down, gives remote control and it provides data for analysis. The physical manual control panels in general cost €200 or more.
The post heater in the Airflow DV145 unit has a PWM (pulse width modulation) heating element control which means that it can control the switching of the heater within a fine tolerance for heating the air rather than just switching the heater On and Off. The reason I installed this was really to provide a back up option to the main house heating system (approximately €200 extra).
House Heating System
The house heating is currently designed around two storage heaters of 1.7 kw each to heat the house using off peak electricity and operate for 7 hours a day. I picked up one unit for free and the other unit cost €70. I suppose one could say that the total capital cost of the heating system was €270 when one adds the HRV post heater.
For the month of October one of these heaters was switched on for 14 days. The post heater also improves the frost protection functionality within the HRV and helps maintain a heating level of 21 degrees Celsius throughout the house.
Below is an example of how the HRV switches on different heating loads in the post heater while maintaining a set temperature . The time interval below is over 60 seconds (full screen view) and the heater appears to adjust the power output required continuously to maintain the set temperature.
Duct work for primary supply and extract
I selected an insulated 210mm EPS duct for the extract pipe as this duct carries the coldest air from the HRV unit .
Supply and Connecting Manifold Ducts
There are a number of options. My understanding is that the larger duct systems such as 150mm feeding multiple rooms with silencers is the best option if one can accommodate this in the build early on and find a good designer. I opted for the 91mm semi rigid ducts using a manifold system from https://www.fraenkische.com and I am very happy with the low noise level and amount of air being delivered throughout the house. I use a co2 sensor to monitor how the flow rates are working in different rooms.
When one is designing a house to the passive house standard or installing an HRV unit in an energy efficient /airtight house one can reduce the cost on the system if one plans the service routes of the ducts early on and selects particular joist types. It is expensive to batten and counter batten to hide the ducts afterwards as one needs to try and keep the duct-work within the airtight envelope.
I opted for the manifold system using the largest semi rigid ducts I could find. These were the Fraenkische-profi-air classic pipe with an internal diameter of 78mm and outside diameter of 91mm. The larger the duct the lower the air friction and noise when delivering air to rooms such as bedrooms. These ducts are also anti-static and low emission.
Below are the choices I came across from the semi rigid range. The white duct is made by Fraenkische.
Connection ducts from Manifold to HRV.
For the ducts that connect between the main HRV unit and the manifold I used an insulated flexible sound reducing duct (as seen below). This is made up of an inner foil with sound reducing properties, next an airtight plastic membrane and then insulation followed by another layer of foil. The inner rim is re-enforced with a steel wire to provide rigidity. It is time consuming connecting this up but it appears to have done its job.