[linuxola] power costs for new versus old devices

[theo.schmidt at wilhelmtux.ch]

Deutsche Zusammenfassung:
Die Energiekosten fpr LTSP können beträchtlich sein. Bei solaren Inselanlagen
dürfte es billiger sein, neue Thin Clients (Verbrauch 10W) zu kaufen, statt 
alte PCs zu benutzen (Verbrauch 40W). Auch im konventionellen Stromnetz 
dürfte sich die Verwendung von alten Röhren-Monitore für den häufigen 
Gebrauch nicht rechnen. Hier müssten vorübergehend neue LCD Monitore gekauft 
werden bis genügend solche sowie Laptops gratis verfügbar werden. Ausserdem 
ist es wichtig, das 12V Netzteil für alte PCs fertig zu entwickeln.

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In last week's workshop at revamp-it in Zürich it was evident that supplying 
adequate electrical power must be an integral part of the LTSP. One of the 
advantages of the LTSP is the robustness: power supply failure to the thin 
clients won't damage anything and only the server must be protected.

However even considering the above, supplying power is always associated with 
costs: investments, running costs and environmental costs. Therefore we must 
consider carefully the power requirements of a LTSP and balance these against 
the costs of supplying power.

Electric energy in Switzerland typically costs 0.2 CHF per kWh, mostly from 
water power. Solar electricity costs about 1 CHF per kWh, but this is for a 
grid-connected system and does not include storage in batteries. The costs 
for solar energy with battery storage are considerably higher, perhaps twice, 
and also involve periodic replacement and recyclcing of the batteries, itself 
a dirty and hazardous business except in the case of sealed plants. The costs 
incurred with diesel generators are also around 0.5-1 CHF per kWh, but there 
is also noise and pollution and this system has no future. Other technologies 
such as fuel cells are becoming available but are still very expensive. Human 
power is suitable for low power levels in remote areas, for individual 
personal devices or for short durations, but higher power levels for longer 
durations would be too expensive and the same would apply to electricity 
generation with animal power.

>From the above it is clear that running the LTSP equipment is costly no matter 
which system is used. The energy costs must be balanced against the equipment 
costs. 

The type of used PCs we are collecting for use as thin clients require a power 
supply of 230V and consume typically about 40W without the monitor. The type 
of CRT monitors we are collecting typically require 100W at 230V.

Therefore operating these devices 6 hours every day typically costs 17.5 CHF 
per year for the PC and 44 CHF for the monitor, in Switzerland. With a solar 
battery installation the costs would however be about 175 CHF per year PC and 
440 CHF per year monitor.

Now we must compare these costs to those incurred by using new equipment. As 
can be seen on the page  
http://www.transtec.ch/CH/D/search.html?q=thin+client&bsubmit=GO
thin clients are available which use 10W or 25W and cost about CHF 350 to CHF 
400. This means that for those areas where the power supply is solar it would 
save costs by buying new 10W thin clients. The used PC thin clients might by 
feasible if the revamp-it 12V power supply can be cheaply perfected and can 
reduce the power from say 40W to 30W by virtue of a higher efficiency.

In the case of monitors, new 15" LCD monitors consuming about 20W are 
available for around CHF 200. Thus it seems that using the available CRT 
monitors is too costly even in Switzerland and probably more so in Africa and 
they should be used only in special cases, e.g. when they are not used many 
hours every day.

It appears that we should carefully consider which devices are used where and 
use new devices rather than used ones in some cases. Special prudence is 
required in the case of CRT monitors. Soon there will be more used laptops 
and LCD monitors available, so revamp-it and others might be advised to not 
collect too many old CRT monitors.

Theo Schmidt