Hello Donald,

----- Original Message -----
From: "Donald Allwright" <donald_allwright@...>
To: <biofuel@yahoogroups.com>
Sent: Friday, September 03, 2004 2:50 PM
Subject: [biofuel] Question - efficiency of sunlight conversion

> I have a question that some of you might be able to shed some light on.

> As well as having an interest in biofuels, I also have an interest in
> Third World development issues and other technologies, including Solar
> energy collection and storage. So when trying to find an 'energy
> solution' for a remote village for example, there are a number of
> possible options. Of course, you have to ask, "what problem are you
> looking to find a solution for?" For the purposes of this post, I will
> assume that we are trying to provide electricity to power
> refrigerators, lighting, miscellaneous equipment such as telephones and
> computers (even remote villages can have satellite connections to the
> internet these days!). This would be a light load and not include
> industrial use nor electrical heating/cooking.

> So I will propose two solutions, both of which are used in various
> places:

> 1) Grow an oil crop, use it to power a diesel generator
> 2) Install photovoltaic solar panels and use a battery system to store
> the energy overnight

You can also gasify biomass and use the gas for generating power
with gas engine or diesel generators. These plants can be configured from 20
kWe to 2
MWe or higher in multiple modules with improved efficiencies for larger
capacities. In a recent exercise we did with UNIDO in Zambia, we discovered
that power cost (1 MW) in a remote location using high cost diesel in this
land locked country with no indigenous petroleum refinery was about US c 25,
while the power cost using gasification was about US c 6-8. The entire
biomass requirements could be sourced from the trimmings from the nearby
forest within a 10 km range.

You could also methanate it into biogas and generate power.
> Now I'm trying to get an understanding of the pros and cons of these
> two approaches, and which would be better for a particular location.
> The issues I have thought of so far are the following:

> Photovoltaics and batteries are expensive in terms of capital outlay,
> whereas biofuels are cheap to 'install'.

> Photovoltaic systems have a conversion efficiency of ~10% of the solar
> energy, whereas biofuels have a conversion efficiency of about 1%

I presume you have factored in the very low "natural" photosynthetic
efficiency of biomass conversion. But this does not have a direct economic
implication in terms of cost of power generated, unlike in PV systems where
the lower conversion efficiencies of a high per kW cost plant with limited
energy resource availability has a more direct economic impact.

> Photovoltaic systems require more specialist knowledge to maintain,
> whereas biofuels require less.

> Photovoltaics require low labour input once they are installed, whereas
> biofuels require planting, harvesting, processing etc..

But the flip side of the coin is that it generates more economic activity a
tht rural level, improving the purchasing power of the community.

> Photovoltaic systems can store only small amounts of energy over short
> timescales, whereas you can store large quantities of oil for a long
> time

So can other biofuels.

> Photovoltaics make less sense when sunshine levels are highly
> unpredictable, whereas biofuel crops are not significantly affected by
> a few gloomy days

Quite true. Sweden meets more than 30% of its energy needs from biomass.

> Photovoltaics require less land to install than oil crops, because of
> their higher conversion efficiency.

The annual accretion of biomass globally is of the order of 25-35 (?)
billlion
MT and represents a little appreciated but highly significant energy
resource. About 50% of the world population still relies on biomass for its
daily cooking and heating needs. All this is being done sustainably since,
despite the growing demand,
" The woods are lovely, dark and deep. And miles to go. . . ."
testifying to its sustainability.

> I realise that this is an oversimplification of the issues, and I'm
> trying to gain a deeper understanding of the secondary issues. So my
> specific questions are:

> 1) What are the implications of manufacturing Solar collectors,
> batteries, electronic control equipment and so forth in terms of energy
> use, toxic materials (e.g. lead in batteries), sustainability? How does
> this compare with manufacturing a diesel generating system?

You have raised very important lifecycle impact questions, an area where
much research is necessary. Thanks for bringing them up.

> 2) Biofuels are often produced from crops that are grown in an
> unsustainable manner. What are the effects on biodiversity of this? How
> can this be counteracted? Are there any comparable environmental issues
> in the manufacture of solar systems?

We need to rotate crops that are indigenous which are familiar to the local
population to best fit the demand and supply. If it is done after careful
study, biodiverstiy can still be preserved. Since it is one off, the
manufacture of solar PV may not involve as much direct environmental impact
as
biofuels either positively or otherwise.

> 3) Do the levels of expertise required to install and maintain a solar
> system make it inappropriate for use in remote villages?

On the contrary. Our experience in India has been quite encouraging.
http://mnes.nic.in/paper.htm

The paper gives an overview of the photovoltaic programme in India and
discusses the potential for future growth

"ABSTRACT : The Indian photovoltaic programme is one of the largest national
programmes in the world. The Indian Ministry of Non-conventional Energy
Sources has been implementing a comprehensive programme for research,
development, demonstration and utilization of solar photovoltaics in India.
The use of photovoltaic systems for lighting, water pumping and power
supply, particularly in rural areas is supported by the Government. A
number of applications in sectors such as telecommunications, railways, oil
and gas and broadcasting have reached the stage of commercial utilization.
With more than 900,000 PV systems, with an aggregate capacity of about 80
MW, India is one of the leading countries in the world engaged in the
deployment of distributed PV systems. The Ministry is also planning to take
up a new programme for the electrification of 18,000 remote villages in the
country. This and other initiatives are likely to lead to a significant
growth in the future. Production of solar cells and modules in the country
during 2000-2001 exceeded 14 MW and 17 MW respectively. The cumulative
domestic production is expected to cross 100 MW level during 2002. During
the 10th Five Year Plan, 2002-2007, it is estimated that another 200 MW
capacity would be added. "

However, the problem in a subsistence economy starts only when high cost
batteries have to be replaced at the end of their lifecycle.

> 4) Am I correct in assuming that the best (cheapest over all) solution
> for a Diesel generator in such situations is to use SVO (straight
> vegetable oil) with a preheating system, rather than converting it to
> biodiesel?

Diesel replacement in a dual fuel mode with producer gas from biomasss
gasification and biogas from methanation are cost effective alternatives.

> 5) What are the effects on electricity usage patterns for each type of
> supply? For example, if people know that their battery system can only
> store a fixed amount that won't be replenished until the next day, are
> they more efficiency conscious than if they know their supply won't be
> replenished until next year's harvest?

Farmers are by and large highly conservationsist in their approach (not so
much efficiency conscious). Our experience with solar lanterns for rural
homes and PV street lights is that users conserve even their reading hours.

> My gut feeling is that due to the higher conversion efficiency of solar
> panels, these would make a better overall solution for providing
> electricity than growing biofuels, with less environmental impact
> overall. However the high capital cost may rule this solution out for
> smaller villages. (Of course if you are using the energy for transport,
> then biofuels are much better because the energy can easily be stored
> and transported over long timescales. But that is not what I'm
> interested in here).

> Does anyone have any other information, opinions, experience of these
> types of systems? Have I overlooked any significant arguments on either
> side?
>
> I may soon have an opportunity to visit a remote solar installation
> that is backed up with a Diesel generator (as far as I know using
> petrodiesel) so wish to find out as much as possible beforehand.
>
> Regards,
> Donald
>