EcoBuild: Photovoltaic, PVT Vs PV or PT

Photovoltaic Thermal:: EcoBuild Expo Update

At the Ecobuild expo, there were a LOT of companies who had photovoltaic elec or water heating systems.  Few were combined PVT (both electricity and heating water). So I started asking why. Speaking to those that make the panesl and installers / advisors the consistent reply was that the reduction in output of both systems was more than 50% down on what you’d get if each was stand alone. One company that produced PV and PT panels said that:

  • A PV panel could produce around 280 Watts  of elec, a PVT panel about 120 Watts
  • A PT panel over 200 (I think degrees) water, but only 40 degrees from PVT.

Yes, it’s still good to cool down PV panels, with ventilation, or even surrounding green roofing. But it seems that cooling them, by linking in pipes to generate hot water doesn’t work. It seems that the temp hot water panels work at is so high to be efficient, that takes out too much electricity production. Or you compromise the amount of hot water production by having the panels at a much lower temp. ie to be efficient they both operate at vastly different temperatures.

So that means looking at seperate systems for electricity production (PV), hot water productin (PT) and something for when the sun isn’t shining for hot water (for taps and heating).

 

EcoBuild: Air Source Heat Pumps

Air Source Heat Pumps

The installers / advisors to projects that were speaking at the lectures for self builders were all very positive about air source heat pumps in terms of how they work and how they stack up from an environmental / energy / sustainable point of view.

There are now automated systems for (for example) an air source heat pump to kick in when Photo Voltaic (PV) panels are producing more electricity than the house is using, and so at those times top up the water thermal store in the building. This can then be used for hot water or heating (under floor works at lower temps) at other times (if needed).

EcoBuild: Waste Water / Drain Water / Shower, Heat Recovery

At Passivhaus levels of energy efficiency hot water accounts for more energy than space heating.

At last weeks Ecobuild, I saw a couple of systems that do this. They capture the heat from hot water that is going down the drain and feed it back into the hot water system. It seems there are 2 systems:

  1. A vertical pipe that the hot water flows down, usually slowed, around the cold water mains supply. Their is heat exchange from the waste water to the cold water, that, in these systems typically, feeds into the water heater / hot water tank.

  2. A system linked to just the shower. So that the heat in the shower waste is immediately put back into the shower. As most showers have a thermostatic valve, this means an instant and guaranteed gain.

+ & – Thoughts

Check the cost of the system Vs the predicted and probable saving for an evaluation of how long the system will take to pay for itself.

  • One of the 2 systems at Ecobuild was the, €299 retail price, system, that you can see at http://zypho.eu/english.html. So price wise, VERY worth considering,  but need to see if:
    • Have to use, what looked like, the integrated shower tray cap / valve bit, or can this work with any shower tray and it’s drainage inlet?
    • Will it cope with sand if used as the post surf outside shower?
    • What is the cost implication of this on each shower Vs a system that copes with multiple showers and other hot water drain pipes (bath, washing machine, dish washer).
    • Does it reduce the cold water pressure? (Does this matter ?)
      I’ve emailed Zypho these questions 
    • Nice write up on the Zypho unit at Ecobuild on the HardHouse blog by Mark.
      – looks good, but questions the heat exchanger and it isn’t yet fully UK approved.
  • Cost Implications:

If used for an external, post surfing, shower, will the system cope with sand, mud, dirt etc?
– it does look like the  Bristol based shower tray system could be put in post a sand trap !
– could even have this bit under the floor in the house and not outside where the cold, frosts etc. could be a problem. It could then also link in to the water outflow from the washing machine, dishwasher and any other ground water outflows of warm / hot water.
–  http://shower-save.com/Joomla_SS/pdfs/Adaptor%20to%2040mm%20for%20RT1-e.pdf
–  http://shower-save.com/pdfs/Recoh-Tray%20grey%20water%20heat%20recovery.pdf

It seems that if you could get a single whole house heat recovery system that auto feeds the cold water supply to showers, and if they aren’t being used sends the preheated cold water to the water boiler (if it’s not full) would be the best. See the schematic below from http://www.gfxtechnology.com/H-3.pdf

This is also how it’s been set up in the schematic at Bristol (UK) based  http://shower-save.com/
 – also see animation they have at http://content.wavin.com/WAXUK.NSF/pages/Certus-ShowerSave-Animation-EN/$FILE/ShowerSave.swf

UK Water Heat Recovery Supplier Listing:

Test Data for Recoh Units:

From http://shower-save.com/gastec.html

  • Recoh-vert 61.2% efficient, with a mixer shower
  • Recoh-tray is 46.9% efficient, with a mixer shower

Shower-Save is even more efficient with a low flow rate or electric shower:

  • Recoh-vert 64.0% efficient with electric or other low flowrate shower
  • Recoh-tray is 52.6% efficient with electric or other low flowrate shower

Schematics of Waste Water Heat Recovery Systems

Notes from other Websites re these systems:

From http://www.gfxtechnology.com/H-3.pdf:

  • Typically, 80–90 percent of the energy used to heat water in the home goes down the drain. Heat exchangers capture some of the heat in drain-water, allowing it to be reused by incoming water. One type, called a gravity film exchange drain-water heat recovery system, has been found to save 25–30 percent of total water-heating energy needed.
  • This technology is compatible with all types of water heating systems, but it is especially suitable with on-demand water heaters and solar thermal systems. Prices range from $300–400 and paybacks are in the range of 2.5 to 7 years, depending on how often it is used.

From http://www.renewability.com/power_pipe/index.html:

  • Falling film heat exchangers have been around for decades. Other than utilizing the “falling film” effect, however, the Power-Pipe® has little in common with other Drain Water Heat Recovery (DWHR) devices.
  • First generation units suffer from high water pressure loss in the freshwater supply, which causes flow problems. Second generation units resolve the pressure loss issue by adopting a non-counter flow heat exchanger design, which delivers a low heat transfer performance.

Other Water Heat Exchange Systems & Discussions:

From Earth Save Products (bottom of the page) their Heat Squirrel – 120ltr heat recovery vessel (for domestic waste water)

Change Your Behaviour – Bath water heat recovery

One behavioural solution to waste water heat recovery, is to just leave a hot bath, hot sink of water full to cool down and transfer it’s heat to the room(s) before you pull the plug. How often do we pull the plug on a bath of hot water to let that heat head off down the drain, when we could let it cool down (ie heat the interior or the house) first ?

Life cycle of window materials – energy consumption and environmental impacts

A great report by the School of Engineering at Napier University in Edinburgh on windows:

Frames of different materials have been assessed on the basis of their production, energy consumption and environmental impacts.

The investigation shows that aluminium and PVC frames exhibit large amounts of
environmental burdens. Accelerated ageing tests have been carried out to test the
durability of windows against weathering impacts. These tests show that aluminium clad timber windows are comparatively least affected by environmental impacts.

CONCLUSIONS (from the article)

  • Aluminium frames cause the highest burden to the environment because of the dangerous pollutants release and high energy consumption during aluminium production. PVC contributes large amounts of poisonous pollutants throughout its life cycle, while timber window frames have the least environmental burdens.
  • Embodied energy analysis has been carried out for a standard 1.2m × 1.2m window. Aluminium windows have the highest embodied energy, amounting to 6GJ. PVC, Al-clad timber and timber windows have embodied energy of 2980MJ, 1460MJ and 995MJ respectively.
  • All frame materials deteriorate to various degrees by environmental impacts. PVC is sensitive towards heat and UV radiation. Timber if not frequently treated, can easily be affected by environment. Aluminium, if not protected well by coatings, gets damaged under corrosive conditions especially in coastal and industrial areas. Al-clad frames are unlikely to deteriorate due to their protective coatings and appear to be the best choice from this point of view.
  • A survey analysis shows that aluminium and timber windows can easily last more than 40 years. Al-clad timber being new on the market, is expected to have a service life well over 40 years. PVC windows, in most cases, are reported to have an optimum service life of 25 years.

Winter Driving Rain May Increase

OK, we know that man made climate change is here, but don’t know how much the systems will tip it to being worse or to self regulate (or stay on the current trajectory).

But it does mean, that on top of it being a very exposed site, there is the potential for driving rain to increase. See the map below, taken from www.innovateuk.org (PDF).

Talking to surrounding residents, that also look out over Perranporth beach, they all say the site gets a full weather beating on a regular basis. The www.innovateuk.org (PDF) recommends the following detailing, that I’m sure ra-studio are already on top of:

  • recessed window and door reveals
  • projecting cills with drips
  • render finishes
  • extended eaves
  • greater laps and fixings to roof and cladding fixings
  • avoidance of fully filled cavities.
There is also (apparently) the issue that materials may behave differently. Again, I’ll leave that to Robert at ra-studio.

Perranporth Beach Clean

As reported in the local newspaper, the West Britton:

Following comments by many Perranporth residents and visitors that the beach was getting in a state, a number of locals used the “Please listen Perranporth Parish Council” Facebook group to short circuit officialdom and self organise a beach clean last Saturday.

With less than 48 hours notice a Facebook event was created and over a dozen people turned up, with their own gloves and bin bags. The participants included Councillor Dave Webster, the local vet, several dogs, children and adults who walking the length of the main beach at high and low tide marks, rapidly filled over a dozen large rubbish bags. One of the ‘finds’ was an enormous fishing net which was pulled, virtually hidden, from the sand.

We popped into the Watering Hole to ask if they were OK for us to put the collected rubbish in their big bins. To which we had a fantastic “Yes, no problem and let me get you guys a drink as a thank you”.

A fun and a fantastic example of the local community solving local problems. Hopefully by keeping the beach clean (the rubbish was mostly items brought in by the sea), it encourages visitors to enjoy the beach and keep it in a good state for others to enjoy.

Average 57% of energy on space heating !!!

According to the Feb 2012 edition of “House & Garden”:

The average British household uses a whopping 57 percent of it’s energy consumption on space-heating, and a further 24 percent on water-heating ….

I hope / suspect this figure is coming down as the “low hanging fruit” of people putting better insulation in existing housing stock and better insulation and seals etc. into new housing stock.

Perranporth Low Carbon Limited ?

Wouldn’t it be great to set-up Perranporth Low Carbon Limited ?

Attending some eco-build talks at the Eden Project, one of the speakers is involved with Hook Norton Low Carbon Limited.

It is an Industrial Provident Society, set up by Low Carbon Hook Norton members to help the community reduce its energy consumption, carbon emissions and save money, with a range of community-based schemes and individual household projects based on interest-free loans.

http://www.hn-lc.org.uk/

From the talk, it seems they coordinated getting funding and then the residents and suppliers to slowly help everybody (residents, the school, local firms ….) benefit (lower fuel bills, jobs to implement the projects …..) and move to a lower carbon / more sustainable village.

In relation to this, it’d probably make sense to chat with http://sustaincornwall.co.uk/ and the linked Cornwall Sustainable Building Trust

Perranporth Low Carbon Limited ?

Wouldn’t it be great to set-up Perranporth Low Carbon Limited ?

Attending some eco-build talks at the Eden Project, one of the speakers is involved with Hook Norton Low Carbon Limited.

It is an Industrial Provident Society, set up by Low Carbon Hook Norton members to help the community reduce its energy consumption, carbon emissions and save money, with a range of community-based schemes and individual household projects based on interest-free loans.

http://www.hn-lc.org.uk/

From the talk, it seems they coordinated getting funding and then the residents and suppliers to slowly help everybody (residents, the school, local firms ….) benefit (lower fuel bills, jobs to implement the projects …..) and move to a lower carbon / more sustainable village.