In Ger­many you need to install an intel­li­gent elec­tric­ity meter if you make larger changes to the elec­tric­ity instal­la­tion in your house (or if you build a new one). At first this sounds inter­est­ing. If you look closer, you need to decide if you want to laugh or to cry.

Such an intel­li­gent elec­tric­ity meter is able to dis­play the cur­rent power con­sump­tion in a dig­i­tal dis­play (if the power con­sump­tion stays the same, you can test with this how much power a spe­cific device needs). It is also able to attribute the power con­sump­tion to dif­fer­ent times of the day. An optional fea­ture (here in Ger­many) is the pos­si­bil­ity to trans­fer cap­tured data to the power com­pany. It is not required that the home-owner is able to see all or even any data from an intel­li­gent elec­tric­ity meter.

The promises are, that with such a device peo­ple could pay less money by using the wash­ing machine or the dish washer or sim­i­lar devices dur­ing times when not much peo­ple want to use energy.

So far so good, but…

• My wash­ing machine or dish washer are about 1 – 3 years old. We did not buy the cheap­est ones, but they do not offer to start the wash­ing upon input from an exter­nal sig­nal or just by acti­vat­ing the power (if they lose power, the cho­sen wash­ing pro­gram is reset to the default pro­gram). Am I sup­posed to buy a new one?
• The power con­sump­tion of all the nec­es­sary infra­struc­ture (dig­i­tal stuff in the elec­tric­ity meter, net­work con­nec­tion to the power com­pany) is not zero, and it is the owner who has to pay for this.
• When every­one is wash­ing when not much peo­ple want to use energy, a lot of peo­ple want to use energy in such moments. It may still help a bit the power com­pa­nies because they do not have to gen­er­ate power (and have expenses because of this) which is not used, but I doubt the con­sumer will get a big reduc­tion then.
• The dura­tion of such power-surplus times with a reduced price may not last dur­ing the com­plete time a wash­ing machine needs. It may be even the case that a high-price time slot may get acti­vated shortly after (if this is done by (mali­cious) intent or not is not even rel­e­vant, as the con­sumer can not do some­thing about it as he is prob­a­bly sleep­ing when this hap­pens in the night).
• The power com­pany may be able to get a detailed trace of what hap­pens in a house (the own­ers are get­ting up at 11am, only take a shower every two weeks, have prob­a­bly a big plasma TV which runs all the day, …).
• I doubt the device is free of secu­rity holes or pro­tected enough against eaves­drop­ping (with all the pro­fil­ing impli­ca­tions, or pos­si­bil­i­ties to manip­u­late the data (pos­i­tively or neg­a­tively) directly in the device before trans­mis­sion to the power company).
• I do not think the most intel­li­gent and consumer-friendly devices will come with enough sta­tis­tics or access-possibilities to really sat­isfy the consumers.

More inter­est­ing would other things which could help cut costs. For exam­ple small low-power net­worked sen­sors which detect if a window/door is open, the tem­per­a­ture in a room, the out­side tem­per­a­ture, the sun­light inten­sity and so on. Together with some actu­a­tors like for exam­ple to close the win­dow, close the shut­ter, change the heat­ing, turn off lamps and so on, it would pro­vide much more imme­di­ate ben­e­fit. In a new build­ing, the net­work could be wired, but in an old build­ing the sen­sors need to be wire­less and battery-powered.

A pos­si­ble solu­tion could be done via blue­tooth v3 in a mesh net­work (yes, if it is not open source, I would also be scep­ti­cal if the com­pany which pro­duces this has enough knowl­edge to make it secure), polled by a cen­tral sta­tion which could put the sen­sors in silent standby to reduce the amount of radio pol­lu­tion and increase bat­tery life­time. If some of the sen­sors and actu­a­tors are con­nected (e.g. room tem­per­a­ture and heat­ing actu­a­tor plus a clock), you could even let it run in autonomous mode (time based heat­ing to a spe­cific tem­per­a­ture) and only need to con­nect to it if there is a spe­cific need. Such a sit­u­a­tion could be that the win­dow sen­sor detects an open win­dow, so the heat­ing can be turned off. Or maybe the sun­light inten­sity sen­sor detects (or the base sta­tion esti­mates) an intensity-rise of the sun­light, so the heat­ing could be reduced in advance.

Some­thing like this would give imme­di­ate ben­e­fit (in com­fort) to those who install it, and in a long-term view it would/could cut the costs down a bit.

I am aware of some wire­less sensors/actuators, but they are rel­a­tively expen­sive, the radio pol­lu­tion (and type) is unknown to me, and the pro­to­col is not open, so I do not know if it is secure and how to improve things I do not like.

Any­one with enough hard­ware knowl­edge and open source/hardware spirit out there to pro­duce a mod­u­lar base for sensors/actuators (blue­tooth + I/O for sensros/actuators/pc-connection + controler)?

I was search­ing for a good heat reser­voir. Unfor­tu­nately it seems that all on the marked are far from state of the art (they are prob­a­bly in their class, but see below).

Most of the devices use water to store the energy. I found one (in Europe/Germany) which is using phase change tech­nol­ogy instead of water to store more heat in the same stor­age place (but you need to ask how much it costs and how long they need to deliver, which prob­a­bly means that it is a lot more expen­sive (partly due to lim­ited amount of pro­duc­tion quan­tity) than water based heat reser­voirs). I have read a lot about phase change mate­ri­als (PCM), and it seems there are dif­fer­ent kinds of sil­ica or wax (or other mate­ri­als) which are bet­ter suited to store heat energy, but the only mass-market tech­nol­ogy seems to be water based ones.

This looks strange to me. When I look at his­tory, other mate­ri­als than water where already used a lot in the past (e.g. stones where heated and then they were used in a press­ing iron or as some­thing which is replaced now by a hot-water bot­tle or an elec­tri­cal heat­ing cush­ion in the bed; yes, all this does not involve a change in the phys­i­cal state of the mate­r­ial, but the point is that other mate­ri­als than water where already used in the past), so I do not under­stand what is pre­vent­ing to let PCM based heat reser­voirs going mainstream.

Except for choos­ing the right PCM and obtain­ing it, it does not look hard to build such a heat reser­voir. You can add a heat-exchanger in the bot­tom and feed solar-power there for long-term heat­ing the PCM, another heat-exchanger at the top to heat the use-water and/or heating-water from the heat stored in the PCM, and a 3^rd heat-exchanger (placed at the top too) which you con­nect to your central-heating if you need a lit­tle bit of quick short-term heat­ing of the PCM. I do not know if you need to add some  heat-layers (e.g. by putting a big cheat of a non-PCM mate­r­ial between the long-term heat­ing part and the short-term heat­ing part), but  it should be easy to test if some­thing like this is ben­e­fi­cial or not. If you have a fire­place which you want to con­nect to the long-term heat­ing of the PCM, it may also be ben­e­fi­cial to have a 4^th heat-exchanger together with the solar-one, but maybe there is another solu­tion to do this with the 3-heat-exchangers-setup (I have not inves­ti­gated this pos­si­bil­ity at all).

If some­one knows some inter­est­ing prod­ucts in Europe or has some help­ful infor­ma­tion (any­thing which can be inte­grated into exist­ing heat­ing sys­tems with­out much ren­o­va­tion of a lot of rooms), please write a comment.

I added two car related items on my ideas page:

• Constant-power cruise con­trol
• Per­sonal GPS tracking

A while ago I got a mail from my bank. They offer to fund a pho­to­voltaic sys­tem on my house with a spe­cial offer. They give a credit upto a spe­cific amount if I use it to install a pho­to­voltaic sys­tem, and to pay it back I just have to give them the com­plete amount of money which I get from the power com­pany when the pho­to­voltaic sys­tem is pro­duc­ing power (the state requires the power com­pany to pay a spe­cific amount of money — fixed dur­ing 20 years — for each kW/h). They also offer that a spe­cial­ist vis­its me to explain the pho­to­voltaic stuff and cal­cu­late if all the phys­i­cal con­straints for such an instal­la­tion are OK.

At first this sounds nice, but I do not trust the words of some ran­dom per­son which wants to get money from me. So I had a deeper look at it.

The roof of my house is still OK, but in some years (maybe 3 – 5) it has to be changed (at least partly). The roof  is already 30 years old, so this is OK. If I would install a pho­to­voltaic sys­tem now, it would have to be removed and rein­stalled when the roof is changed. If the sys­tem is financed by the bank, this has to be done by an offi­cial spe­cial­ist (instead of let­ting a good friend with expe­ri­ence doing it in exchange of my work­force for some ren­o­va­tion project at his house). This means it would be cheaper if I change the roof before the pho­to­voltaic sys­tem is installed. I do not have the money to do this com­pletely out of my pocket, so the bank has to finance this.

Let­ting the cost of the roof aside (which has to be done “soon” any­way), the inter­est­ing part now is what do I get when the bank is com­pletely financ­ing the pho­to­voltaic sys­tem (maybe parts of the elec­tri­cal instal­la­tion need to get updated, as they are 30 years old too). I have to take into account taxes, what needs to be paid back to the bank, what I have to pay for the power, and what I have when every­thing is paid back.

If the pho­to­voltaic sys­tem is financed com­pletely by the bank, the typ­i­cal cal­cu­la­tion is that it takes about 20 years to pay back every­thing. This assumes I only give to the bank the amount of money I get from the power com­pany for the power of the pho­to­voltaic sys­tem. So basi­cally the pho­to­voltaic sys­tem pays itself. This sounds great, the prob­lem is that a rough esti­ma­tion of the life­time of a pho­to­voltaic sys­tem is 20 years (and after 10 years you may have to change the AC con­verter). The war­ranty on pho­to­voltaic ele­ments here is 2 years, so far I have not seen any offer where they extend it much (some­how it is hard to find some good pages for pri­vate cus­tomers, most of the pages I see are either light on info, or tar­get com­mer­cial cus­tomers). This is not even remotely in the range of 20 years. So after it paid back itself to the bank, it may be bro­ken. And dur­ing those 20 years, I still have to pay my com­plete power bill.

There is also a tax point of view to take into account. Luck­ily a friend of my sis­ter is doing some tax con­sult­ing for pri­vate tax issues. The tax stuff involved here is about com­pany taxes (you are required to open a com­pany when you install a pho­to­voltaic sys­tem here). This is not spe­cially in the area where she is work­ing in, but I assumed she should know enough about the basics, that I can get at least an overview. I got even more than that. When I talked to her about it, she told me they cal­cu­lated a sim­i­lar offer for their house recently. She assumed a pho­to­voltaic instal­la­tion of 20 T€ and that the bank is financ­ing it com­pletely. The roof of their house does not have the same char­ac­ter­is­tics than my house, but as the pho­to­voltaic spe­cial­ists cal­cu­late with rough peak sun­shine hours any­way, it gives me a rough overview. The good part is, that you do not lose money this way, but you have to pay the tax directly (even if I give all the money from the power com­pany to the bank), you start to earn money near the end of the 20 years.

Accord­ing to her cal­cu­la­tions you will have earned 6 T€ after 20 years, when the pho­to­voltaic sys­tem paid itself back to the bank and you had to pay the taxes each month/year/whatever. This assumes that the peak sun­shine hours are not get­ting worse, and that the effi­ciency of the pho­to­voltaic sys­tem stays at roughly the same level dur­ing the 20 years. Now let us cal­cu­late the amount of money per month and per year you gain when you do this:

€/year

€/month

So for 25 €/month I have to invest my time into tak­ing care about the tax stuff, have to take care about the pho­to­voltaic sys­tem (clean­ing, and man­age­ment stuff in case some­thing breaks because of bad weather or nor­mal usage), have to pay extra money when some­thing has to be done to the roof, and so on. And when every­thing is fin­ished after 20 years, the pho­to­voltaic sys­tem may be fin­ished too (and the rate of money the power com­pany has to pay for each kW/h then is not known, in case the sys­tem still works good then). If it is in a state where I have to remove or replace it, I also have to pay the cost of remov­ing it. And I need to get together enough money to get a new roof now.

Now this offer does not sound so good any­more (remem­ber, I also have to pay the power I con­sume dur­ing this time). To me it looks like only the bank and the com­pany installing the sys­tem will ben­e­fit from it, and I have to take care about all the unpleas­ant things.

There is for sure an eco­log­i­cal aspect to think about here. It sounds great to pro­duce green energy (I do not know how much CO2 is pro­duced dur­ing the pro­duc­tion of the pho­to­voltaic sys­tem, and if it will pro­duce enough energy to com­pen­sate this), and I would do it directly if I would see a sane return of invest­ment, but this offer does not look sane in my cur­rent situation.

It seems I have to wait until the prices go down more (and I have some spare money to invest with­out the need for a bank). Recently I have read that the expec­ta­tion is that in about 3 – 5 years the tech­nol­ogy to print pho­to­voltaic cells can be pro­duc­tion ready, which could reduce the price to a tenth of what a pho­to­voltaic cell costs ATM. Invest­ing 20 – 30 T€ is not some­thing I would do from one day to another, 4 – 5 T€ for a sim­i­lar instal­la­tion sounds more easy to agree to.

While I am at it: so far I only see pho­to­voltaic info regard­ing the peak power a cell can gen­er­ate. To me this does not look inter­est­ing. The peak power will be gen­er­ated most of the time in sum­mer (direct sun­light, no clouds, long sun­light times), but in the sum­mer the con­sump­tion of power is less than in win­ter (less light to use, more time spend out­side the house so less time in front of a TV, more BBQ so less cook­ing in the kitchen, …). More inter­est­ing to me would be a good power gen­er­a­tion in less than opti­mal sit­u­a­tions like in win­ter when it is cloudy (but it is prob­a­bly hard to come up with an use­ful value, as the aver­age for “less than opti­mal” varies from loca­tion to loca­tion). I have seen a report about water heat­ing (attached to the cen­tral heat­ing) with solar energy, where a sys­tem is used which has a lower peak power, but a bet­ter power out­put in less than opti­mal weather con­di­tions (round col­lec­tors where used instead of flat pan­els). So the­o­ret­i­cally there is the pos­si­bil­ity to get more power out in not so good con­di­tions, but so far I did not find any infor­ma­tion if it is tech­ni­cally pos­si­ble ATM to opti­mize pho­to­voltaic cells to such sit­u­a­tions, and if it is if there are some cells avail­able for a sane price.