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Topics - etienne

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Walking the walk / Fundraising selling organic cotton clothes ?
« on: January 03, 2018, 08:48:22 AM »
I received an advertisement from Rapanui Clothing for their Teemill system which allows people to start their own T-Shirt shop.

Their clothes are full organic and of good quality. Many organisations use the system for fundraising.

So if somebody has artistic competences, this could be an option for fundraising and creating cool clothes.

Here are some examples :

Don't know if this would be an option, but I'm not the artist here.

It's almost free, which means that there is no direct costs, excepted that you need to order the T-shirts you design if you want to publish pictures of them.

Best whishes for 2018 to everybody.


Policy and solutions / Grid data and energy balance.
« on: October 06, 2017, 09:16:28 AM »
I found that I was often a little bit out of topic in the renewable energy topic, so here is a new topic to talk about grid and energy balance.

You will find below the graphs I made per month from the Swiss load curve and I added the cost of the equilibrium current in Luxembourg.

Data come from here :

Here are the other links that have been shared in the renewable energy trend. Sorry for not giving each time who is the "owner".

Walking the walk / Managing PV + battery system
« on: September 20, 2017, 01:43:01 PM »
At work, we just started a PV (20 kWp) + Battery (15kWh) system on a building with 4 appartments  that have heatpump heating (well, appartments are only half full yet), and I have to say that it works better than what I expected. Even now mid September, on rainy days, we have enough electricity until like midnight (heating is only needed for sanitary water yet).
A lot of sun doesn't help much because batteries are full around noon, so we start to use extra tips to use PV electricity in excess.
I started the "what to do with PV electricity in excess topics,2076.0.html when the conception of the regulation was underway. It seems to work fine.
Since most ways of using excess PV electricity are not so efficient or mean higher energy loss (an overheated boiler has over average heat loss), I decided to stop any not needed electricity use during peak hours (around noon and after 16h) in order to support the local electricity network. The idea is also to have some experiences for future smart meters and regulations that might come with them.
Does any body has experiences in that area, some good tips...

Policy and solutions / City or countryside : which direction ?
« on: July 09, 2017, 09:59:53 AM »
Luxembourg is trying very hard to become an international player in whatever is possible. Right now the government is looking for 25 hectares  (1/4 of a sqr km) for a Google datacenter. This is in order to promote digitalisation which seems to be the new trend and to use it as a magnet for other companies. Such a move is only possible with a massive urbanisation of the country. Looks like the aim is to become some kind of Singapore in the center of Europe.
I see many problems in such a move from nature destruction to sustainability (a datacenter is only good for 20 years). I see IT technology as very efficient in a business context and generally for communications, but I’m not so happy with the « gaming » and « hobby » part of the picture, it takes a lot of time out of the kids’ (and adults’) lives and uses a lot of ressources (electricity and electronic devices). Somehow it also reduces local interactions between people since I discuss such topics on a forum instead as with neighbors.
Furthermore everything doesn’t need to be digital, costs have to be in relation with benefits.
It also creates uncontrolled points of failure even if the theory is that the cloud is everywhere.
Do you have any experiences with such investments and policies ?
Thanks, best regards,

Walking the walk / What to do with PV electricity in excess ?
« on: June 13, 2017, 10:45:08 PM »
Does anybody has an usefull idea to use PV electricity in excess when batteries are full, water is hot, washmachines are finished, clothes are dryed and refrigerator/deepfreezers are on supercool/supercold ? Probably 5-6 kW or up to 15 if it really makes sense. The problem is that we are talking of maybe 200 kWh (up to 1000 if it really make sense) per year between May and September and that it must adapt itself to the available power. In the third world countries, I would disinfect or pump water, produce Ice..., but that is not so much needed here in Luxembourg.
Thanks for any idea.

At work, we have projects regarding load balancing in order to see how we could stabilize or move the load in private houses. A lot of technology is available, but there is no incentive. My feeling is that electricity producers need these peak prices in order to balance the budget, and so they don’t really provide the needed information and the incentives to make theses technologies financially interesting.

i’d be very happy if I could get for example off peak electricity 20% cheaper, and peak electricity 20% more expensive. This could be real time information and it would justify all the smart grid technologies that are now available for houses (from batteries to wash machines) but that nobody implements because electricity just has all the time the same price.

Utility Dive has an interesting article bringing up some of the issues.

Best regards,


Walking the walk / Is solar thermal heating out of date ?
« on: June 01, 2017, 05:30:42 PM »

I see always more systems using directly solar electricity to heat sanitary water, I even heard of a system from Solacal using DC current in order to save the inverter costs and losts.

I had an idea to use solar heat without having to change too much my heating system, send it to a supplier and didn't got any answer. See attachment.
Pumps and anti backflow systems are not drawn.

Does anybody has experience with such configurations ? Does it make sense ? Is thermal solar really more expensive than PV solar ?

My feeling was that thermal solar was seen as not so good because panels' surface was most of the time oversized, so ROI (and EROEI - energy return on energy investment) was too low, but looks like things are worse than what I thought.

Thanks for your comments,


Walking the walk / Energy management in a business context
« on: January 13, 2017, 10:34:47 AM »

After doing energy optimisation for 8 years now, I wrote, first in french
than made a fast translation in English
of a document with all my professional experiences regarding energy optimisation.

Comments from sidd (please see first reply) have been integrated in the English version. My e-mail has been removed so that my mailbox is protected if the document in shared. There is a reference to my personnal page which has a contact page.

I thought this might interest you all.

Thank you for all comments, also regarding spelling and gramatics.

Best regards,


Walking the walk / Heating with wood or pellets ? and air heat pump ?
« on: January 04, 2017, 09:18:23 AM »

It's winter time again and we have all these articles saying how terrible wood heating is, even pellets oven would be a catastrophy because of the soot and other small particles that would be sent in the air.

Well, there is a study of the GISS saying that the soot of organic carbon doesn't have an effect on climate, which is not the case for the black carbon (from petrol or coal) :

I also believe that small particles are not all equal when talking of health hazard. When smoking was allowed in pubs in Luxembourg, you could enter in rooms where there really was a smoke cloud. I am pretty sure that if the room would have been filled with the same amount of small particles coming from a diesel engine, nobody would have survived such a frequent exposure.

I agree that wooden fire, like any technical process, needs to be done in good condition (dry and hard wood, efficient stove, not a low burning fire…), but I don’t believe that it is a major issue if smoke enters in the room each time that you have to open the stove to add some wood. There really is an issue regarding the stove quality because many people (like my parents and my parents in law) use very old  or broken stove.

I often have the feeling that people against wood heating are not so objective. The article that were presented to me just mix everything without giving any virtue to wood heating. Looks like there would be some hidden interests behind.

What is your feeling about it ? I ask the question because my wife wants to try one week without wooden fire to see if it changes something in our house.

I also have a comment about the air heat pumps. I always recommend to people installing such a system to have an extra pellets stove because the heat produced by the heat pump is equal to the electricity consumption of the compressor added to the heat absorbed in the air. When the air is very cold, you almost get an electrical heater. Furthermore, the pellet stove could work with batteries if needed.

Thanks for your comments, best regards,


Science / Articles in the press
« on: September 23, 2016, 10:43:29 AM »

Don't know if this is a good idea, but we could have a topic putting together Press articles. There should be as information at least : The title, the publisher, the date of publication and the name of the author.

Only articles you really liked should be indicated, otherwise this list would fill itself too fast. I would also suggest a separated topic for articles that are not for general public.

Here are two articles I liked :

Greenland may be losing ice even faster than we thought - Washington Post 20160921 - Chelsea Harvey
It is about the fact that the loss of ice in Greenland could have been underestimated because of the elevation of the ground when ice melts.

Seas aren’t just rising, scientists say — it’s worse than that. They’re speeding up - Washington Post 20160810 - Chris Mooney
Its about the impact of the Pinatobo eruption on sea level rise and how it mistaked the statistical analysis of sea level rise.

Best regards,


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