The next regular meeting will be on Thursday 14th March 2024 at:
Thus. 14.03.24 at 16:30 and every 8 weeks:
Then Thus. 11.04.24 at 19:30 and every 8 weeks:
Here are some notes from our February meeting, it was nice to see new faces and several old ones, one unlit!
Apologies if anyone found the discussion on battery charging too esoteric.
- How significant are heat domes in new housing developments?
Also called urban heat islands, these can result in health consequences as well as additional energy demand for cooling. The general view was that this applied mainly to larger town/cities when overheating is already a major concern. Appropriate planning rules to improve green spaces/corridors and allow better air circulation are still necessary in smaller urban areas, especially now, given a warming climate.
- The numbers are in! We can now make a statement re charging residential batteries from the grid.
Jules has developed a spreadsheet to calculate this for individual cases, please take a copy to use. I’m hoping we can put this discussion to bed with the following statements, but feel free to comment further:
- In the absence of any other evidence, we’ve agreed to compromise on ‘typical’ round trip efficiency (RTE) for an AC-coupled battery system of 80%. Individual usage may make this higher (~85%) or lower (~75%).
- Charging your battery from surplus PV provides the most effective payback for your battery system. This is what ACT recommends as it also reduces your carbon emissions from the electricity you consume.
- Charging your battery from the grid at a significantly lower tariff (e.g. off-peak period rates) can further reduce the payback, by how much will depend on several factors, such as the relative unit price; number of charging cycles; % of grid charging compared to PV charging.
- ACT does not encourage excessive charging from the grid as this may increase your grid’s Carbon Intensity and reduce the life of your battery. Instead, we recommend a careful analysis of the various parameters to calculate the financial and carbon impacts, before opting for this.
There may be other reasons for charging a residential battery from the grid, e.g. helping reduce demand during peak periods or ensuring sufficient backup energy is available in case of a grid outage. Reducing costs is, however, only possible in a few cases, so it is worth using the calculator above to find out first.
- How well does the finance sector follow the energy hierarchy?
It seems more and more. The headlines we hear tend to be either euphoric trumpeting technological solutions or depressing highlighting the lack of effective action. Often the less dramatic information is not reported. Industry and commerce is well ahead of most governments and even ahead of most people in taking decisive action. Here is an interview as an example of a business focused on the 2nd step of the energy hierarchy.
It would be even better if financial/economic system embraced the 1st and most effective step in the hierarchy, namely cutting out waste. We can do much to reduce (not eliminate) the 67/70 % inefficiency in energy systems (Europe/USA respectively), but we could also eliminate 25-50% unnecessary (wasteful) energy use which is more widespread in homes/businesses than we think. Unfortunately, there is no money to be made in using less energy and behavioural change is challenging for most people.
- Scope-3 and carbon factors, sources and how we use them.
We are updating the carbon factors used in the CFT and associated lookup tools. Look out for an adjustment to some of these. If you are interested in joining the discussion to include different ways of calculating ghg emissions caused by our everyday activities, please contact Fuad.
- Hot water tanks and how best to heat them.
Hot water accounts for ~20% of total heat energy used in the home. The question on how to ‘best’ heat this when there are several choices comes up quite often. Heat Pump (HP) owners often ask this question because of the reduced performance when heating domestic hot water. Quite a few people have PV diverters that channel surplus electricity to the immersion element.
It is sometimes tricky to work out the actual hot water energy consumption in a domestic setting. This becomes more difficult in a public setting because planned consumption can vary a lot. This is where energy assessment programmes like TECs’ E-Pack can help.
Advice on this will depend on the objective and circumstances, so these need to be established first. As a starting point, always use the energy hierarchy shown on our webpage. That is only heat as much water as you need and only when you need it. This often reduces energy consumption by a significant amount, up to 50% when inadequate heating controls are used.
We discussed a couple of scenarios to see if it is possible to work out how to heat the required water using different technologies. You can find a number of calculated actions in relation to heating water from the CFT results help panel, search for “hot water” in the ‘list of actions’ tool (make sure you select the year 2023).
- Vertically mounted PV panels.
There are few advantages of vertically mounted PV panels. In the right orientation and with no obstruction low winter sun, they are likely to perform better in the winter but this is a marginal gain. Overall, their annual output will be lower than an equivalent roof mounted system.
Planning rules apply equally to both roof and wall mounted domestic panels. It is, however, worth checking with the respective planning authority (TDC) and of course any immediate neighbours that may be affected. A number of people at the meeting expressed their experience that rules seemed to differ between different planning officers. A case for asking for a copy of the applicable regulation?
- New study on domestic wood burners.
This study focuses on airborne pollutants like PM2.5 and other toxic emissions. This topic is discussed from time to time at the Energy group meetings. ACT has also published an article on the topic in early 2021, this generated several comments.
The general advice is, but each case can be different:
- Burn wood as a primary source of heat generation, so basically using a biomass boiler, avoid room burners unless your home is a cabin in the woods.
- Know the source of your wood to ensure ecological sustainability and associated ghg emissions.
- Ensure your wood is of the correct quality to minimise health impairing VOC, NOx or PM emissions.
- Take appropriate precautions to minimise serious health impairing emissions both indoors/outdoors. Urban areas are the most challenging.
- Adhere to the latest regulations on sourcing biomass and on devices that burn these.
- Do e-mails produce more ghg emissions than paper?
Good question. We try to provide tools to help users make more informed decisions, often by comparing the impact of one or more options for doing/buying something, see the reference to these tools above. Unfortunately, it’s not possible to populate the tools for all things as it sometimes takes a lot of research to get to a ‘good’ answer.
Luckily, we can usually find one or more ‘good’ references which we qualify to make sure they give a representative value for ghg emissions. In this case Jules had “How Bad are Bananas” on hand.
It turns out e-mails and a sheet of paper, especially scrap paper, produce tiny amounts of ghg emissions (a fraction of a gramme CO2e). For e-mails, most of this is related to making/using the computer. When most of us have an annual ghg footprint of 10-20 tonnes, should we not be looking elsewhere for quick and effective reductions?
Nevertheless, we do send a lot of e-mails (and paper if we used this), so it’s good to follow the energy hierarchy mentioned above. That is avoid unnecessary e-mail recipients, think about who needs to receive it and can you reduce the size of attached files (e.g. pictures).
Written by Fuad
Energy group coordinator
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