We round up some of the best comments that have appeared on the new look BSJ website in the past two months

PV costs

Story: Concentrated solar power plants in North Africa could supply Europe

Comment 1: from Nick Cook.

"I was interested to note your comment about viability of renewable technologies re "Unfortunately, unlike heating, the options are very limited, the most common ones being photovoltaic panels and wind turbines. However, the viability of such devices is very sensitive to location"

An interesting example of non-viable photo-voltaic's I found recently is the CIS building in Manchester, (details can be found at Solar century website).

Doing the calculations from the figures given for the £5.5M project, the installed cost comes to about £14/Watt, about 10 times the generally accepted viable cost. If the project was undertaken on a purely commercial basis (e.g. capital had to be borrowed at say 8% with pay back over 20 years) then the cost per KWh works out to about £3, about 20x current grid cost.

My argument with regard to this sort of green flag waving is that it would be far better to put £1M in the bank to cover the cost of 20 years electricity and spend the remaining £4.5M in areas such as; R&D to speed up the development of cost effective PV, investing in DESERTEC type schemes, etc."

Comment 2

from Alan Taylor Politicians are not engineers and have no idea of the impact of their policies. They are clearly getting the wrong advice form the Whithall Mandarines. The engineering community needs to make the business case to Parliament and the EU. There is also the question of getting the African countries to agree to these installations and country stability must be a serious issue to resolve here otherwise the risk is argueably too high. A very high benefit to the host country should also be factored in to the business case in the form of improved power infrastructure and water distibution and quality across other African countries to assist buy in to the programme.

Better management please

Story: Why Projects are delayed
Comment: from Richard Hall

I am a former mechanical contractor who has moved into consultancy. The M&E services are normally the last item to be finished an can hold up the project I would say this is normally always down to poor management on site. Project that have set DTM's with agenda and a strong co-ordination manager are much more likely to complete on time.

If the construction is more complex the building contractor will normally spend less time with the M&E sub contractor as they are concentrating on the build with fingers crossed that all will come together.

Wasted energy

Story CPD Module S4: The use of heat pumps with radiators

Comment By: Bill Clark.

A comment on a quote from the article 'However, the advantages of heat pumps are that they do not directly use fossil fuel, so their greenhouse emissions will be less than a conventional boiler, if they use less comparable electricity and/or, if green electricity can be utilised'.

Perhaps it would give a more balanced rather than bias view to note that the average efficiency of UK generation, transmission and distribution of electricity is around 38% so that in reality use of such technology is not actually reducing CO2 emissions, rather it is simply relocating (geographically) the point of emission back to the power station.

If CO2 reductions are the driver then it becomes advantageous to stop burning gas in power stations to generate electricity and burn it locally either in high efficiency gas boilers or if heat pumps are required (and they have their place) then better to use gas absorption types.

POE at schools

Story The aims of CIBSE's newly launched School Design Group explained by members, from Building Services Journal

Comment By: Nat Stott I think this is a vitally important issue in our aim to reduce carbon emissions and applies to more than schools. This sort of post occupancy evaluation needs to be applied to a range of new buildings so that clients can learn what low carbon really means. Does the CIBSE schools group have a mailing list yet? I can't find one.

Any answers?

Story: Solar heating:

Comment By: Jittu Cherian

I have a few queries regarding solar water heating.

1) I would like to know tha amount of energy that I can get from a 1x1 sq.m of panel?

2) What would it cost me to install it in a normal G+7 apartment block in the Middle east ?What would the pay back period be on such an investment?

3) The solar water heaters are maintained to about 50 - 60 deg. C and that means the conditions for Legionelle bacteria to survive is at its best, so what are the options that should be taken to prevent such bacterial growth? In one of the CPD modules the different ways to detect Legionnaire's diseases was explained, similarly a section to prevent such a disease would be more valuable I believe.

Hope to receive some satisfactory responses soon.