Aa: Assess and analyse

The crucial thing when aiming for a sustainable energy system is to combine the renewable resources with the desires of the end user.

The link between these two ends is the (commercial) energy carrier. The energy carrier must fit both ends so that the resource is well aimed to produce the energy carrier at maximum efficiency and so that the end user can take full advantage of the energy carrier to get the energy service desired. All three must always be part of the analysis – if not, the system will be inefficient.

These analyses do not have to be detailed but they need be done not to forget important aspects. To help, you will find a number of general examples if you click your way through the matrix.


Bb: Basics of biomass

Biomass is already dominant, together with hydropower, among the renewable energy sources and most scenarios indicate is will stay so. In many cases people tend to mistake “biomass” for “dedicated energy crops grown on agricultural land” but that is a misconception. Biomass for energy purposes does not have to be virgin, it does not have to be exclusive and it may well originate from cities.

Organic waste, vegetable residual oil, park trimmings and clippings, garden waste, sewage sludge – the number of biomasses found in modern society is huge.


Cc: Careful cycling

Solid household and municipal waste consists of clothes (cellulose fibre), paper, garden waste, park clippings and lots of other things that could best be used as fuel in modern waste incineration plants. To be useful, the suitable fractions must be separate and clean and waste separation and handling is an absolute necessity and should be an integrated part in a sustainable energy system.


Dd: Dumps and digestibles

Anaerobic digestion is a natural and spontaneous process occurring not only in dedicated reactor tanks but anywhere where conditions happen to be favourable. One such place is waste landfills and dumps.

Digging down perforated tubes at the bottom of the landfill one will be able to extract significant amounts of biogas – in this application called landfill gas – to be used in CHP-production using for example IC-engines.


Ee: Efficiency everywhere

Planning for RES is to plan for a sustainable future energy system.

For something to be sustainable it must be socially, economically and ecologically sustainable.

As a global average todays’ energy system consumes approximately 100 kWh of natural resources to provide the end-user with 20 kWh of useful energy. One main reason is the low-efficiency processes commonly used to produce electricity, another is that energy is often used in inefficient ways and wasted. Paramount in the planning process is therefore not only to fit the energy carrier to the energy source but also to fit the energy carrier to the energy needs.

Consequently, energy saving measures and optimisation at the end-user also come in as some of the most important factors in the over-all system analysis.


Ff: Forest fires

The current climate change has as one side effect that hot and dry periods are becoming more and more frequent in Europe and this tends to increase the risk for forest fires. With a proper forest management, including removal of residues and dead material, this risk can be managed. The residues should of course be removed with due consideration of the demands for biological diversity and should be used for fuel.


Gg: Gasification is glorious – or?

Gasification is sometimes useful – sometimes not. There is an over-sell of gasification processes as if that would solve everything, but look at this example:

Say you start with 1 kg of wet and dirty wood: 0.45 kg of water, 0.05 kg of ashes and 0.50 kg of the real stuff – dry wood. This will contain 2.55 kWh in total, i.e. 2.55 kWh/kg feedstock.

Put it into a gasifier with no losses at all at 700 oC together with 1/2 m3 (0.64 kg) of air.

To boil off the water you will need 0.3 kWh, to heat up the gas you will use 0.35 kWh and what is left is then 1.9 kWh as chemically bound energy in the product gas. Assuming 40 g of the ash to be left in the gasifier, the total gas will then be 1.60 kg yielding a fuel gas with lower ash content than the feedstock but not ash-free, with a water content (in the form of steam) 28 % by weight and with a heating value just below 1.2 kWh/kg, just less than 1.4 kWh/kg if the sensible heat in the gas is included.

If someone considers that gas a significantly better fuel than the original feedstock and is willing to pay you the full cost to perform the process – bid them welcome!


Hh: Home heating

A significant amount of the total energy used in modern society is used for space heating in buildings including individual households. Thermodynamically, space heating is a low-exergy energy service and to maintain the highest possible efficiency throughout the energy system it should thus be supplied using a low-exergy energy carrier.

The most efficient way to do this is by district heating and cooling systems. Such systems will also provide for the use of several different renewable energy sources in a clean way.


Ii: Industrial incentives

Process industry – steelworks, glassworks, biotechnical factories, chemical industry, food processing and manufacturing … – will prefer to use an energy carrier that is clean, easy to control, and reliable. Hence, the choice is often electricity or gas regardless of what the process really requires.

Part of the planning for new and renewable energy is to actually analyse what the real needs are and to promote a switch from the traditional energy carriers to new ones. This will require an economic incentive like an investment subsidy or alike, something that should be instrumented on federal (EU) level.


Jj: January and june

With the climate change, the needs for cooling during summers is increasing. At the same time, hot periods are also those when the cooling towers used with condensing power production stations are the least efficient so that the efficiency in electricity production is at its lowest.

Since climate cooling is today mainly produced using electricity-consuming AC-units in individual houses and apartments, this results in a peak demand for electricity at the same time as there is a dip in production.

There are two ways to meet this discrepancy: Change the cooling systems from electricity demanding into tri-generation district cooling, which will also increase the total electricity production, or just go on expanding the electricity production using todays’ technology. The latter is what is foreseen in the federal scenario “Energy roadmap 2050”, the former is what is recommended in the present material.


Kk: Kitchens and kerbside collection

Most statistics agree that we in the rich countries lose almost 30 % of the food we import as waste along the supply chain from importer to dinner table.

Though you might not think of it the consequence is that population centres like cities are actually a source of biodegradable organic material. Just imagine how much organic material will actually be “produced” on a daily basis in London!

As a very general rule of thumb for European cities – this is not valid for sprawled American conditions – you may imagine that the total biogas potential, all included, from an urban area, is the same order of magnitude as what the public transport system in that same area requires…


Ll: Local liaisons

For social sustainability it is important to – as far as possible – engage local entrepreneurs for the supply of fuel to local energy plants.

With a proper biofuel mix for a local CHP-plant a long-term additional income can be created for forest owners and for agriculture.

At the same time, a proper energy system solution is part of municipal waste management and may provide savings in the waste management system. Also transportation will be needed and again that will create local, long term jobs. Similar but different local job opportunities will come with other types of RES use. To get started one will also have to work in close connection with the local politicians for planning permissions and such.


Mm: Mastering money

When presenting RES projects to credible, capable and creditworthy sponsors, they will focus on a number of key areas for their judgment. Your presentation must therefore concentrate on these areas. The most complex RES-chain is the one including biomass as a fuel so this is the one selected to serve as an example and then the key areas are usually these:

  • Feedstock supply
  • Feedstock storage, transportation, handling and treatment
  • Biomass conversion to energy (gas, electricity, heat or cooling)
  • Construction risks
  • Energy offtake contracts

Generally banks will want a minimum of four of these five elements to be fully proven with reference projects demonstrating a first class track record.

For other RES projects such as wind-power installations the number of points will be less and different but before sponsors are approached you should see to that you can answer questions like these.


Nn: Noise and neighbours

With wind-power stations one concern during the planning phase is often the fear of noise from the neighbours. But noise is not only a problem with wind-power installations. The transport and filling of hoppers for wood chips or pellets is another example of a local disturbance that needs to be taken into due account when a local installation is planned.


Oo: Organic oils

Looking into it one may well find that the total amounts of used frying oil and other fatty residues from city areas is significant. Getting rid of these residues is also often a problem for the restaurants.

Collecting the oil residues from households, restaurants, food processing industries and agricultural activities may well provide a sufficient basis for a local biodiesel production.


Pp: Practical planning

The energy sector is one where innovators are plentiful and there is a number of different ideas and patents for processes.

When planning for a new energy supply system it may seem tempting to look for the most innovative and spear-head technology but one should be aware that sponsors will usually be reluctant to put their money into high-risk projects. So during the planning phase, be sure to make your referencing to existing and operating plants, not only to high-flying plans. The “t” makes a huge difference in the credibility of your own plan.


Qq: Qualified questionings

Once plans are advancing there will be the time for public hearings and then each and every assumption and conclusion of the project will be questioned. Remember that once office hours are over everyone – university professors, Nobel-prize laureates, the editors of high-ranked scientific journals – are “public”.

The width and depth of the competence found with the audience at such hearings will usually be far beyond that of the project leader and you are given access to it for free. Such hearings should be used and set up to collect input to the project rather than being regarded as something evil but necessary.


Rr: Renewable resources

Resources come in three major forms:

  • Stored. Think of them as a bank account with a certain capital, no payments and no or a very low interest. Each withdrawal will reduce the capital/resource. These are not renewable. Coal, oil, uranium and fossil gas belong here.
  • Funded. Think of them as a bank account with a certain capital, regular payment and with an interest. Managed with care the capital/resource can last forever. These are renewable. Biomass and hydro-energy (replenished by rain) belong here.
  • Flowing. Think of them as a hole in your pocket so that no money can be kept. Like a sunbeam they must be caught in flight. These are renewable. Wind and solar energy belong here.


Ss: Safe storage

Biomass and biofuels are living materials. Even wood pellets are biologically and chemically active.

When pellets are stored in a closed compartment, a silo or the hold of a cargo ship, then the atmosphere will successively be depleted from oxygen. When fresh biomass is stored in piles, micro-organisms including mould will establish and cause heating which may lead to self-ignition. Even if the pile does not self-ignite, there will be spores that may cause allergic reactions once the material is handled.

To put it short: The logistics of biomass are complicated and includes several risks that must be taken seriously.


Tt: Tiny thermodynamics

Energy comes in two forms, exergy and anergy, and the total energy is the sum of both.

Exergy is the energy that can be transformed into other forms of energy.

Anergy is the end result of the transformation.

Electric energy is approximately 98 % exergy and 2 % anergy. So if there is 100 kWh of electrical energy, then that is 98 kWh of exergy and 2 kWh of anergy. To produce this electrical energy, the primary resource must then provide at the very least 98 kWh of exergy.

The energy in flowing water is also about 98 % exergy and we have the technology to take the exergy from the water and put it into the electricity grid at a very high efficiency. So one can say that starting from 100 kWh of exergy in flowing water (and then there would be just above 2 kWh of anergy too, making up 102 kWh of energy in the water) we may produce 98 kWh of electrical exergy and then 2 kWh of the exergy in the water will have been converted to anergy that also goes with the electricity.

The energy in the blowing wind is also almost pure exergy but there comes another limitation known as the Betz limit, saying that no more than about 60 % of the energy can be converted into electricity. So to produce 100 kWh of electrical energy the wind must supply almost 170 kWh.

Solar radiation is also almost pure exergy but in that case we do not have the technology to fully use it for electricity, todays solar cells have efficiencies less than 25 %. So to obtain 100 kWh of electrical energy one has to collect at least 400 kWh of sunshine.

These are facts that cannot be negotiated. For global resource housekeeping, it is therefore important that the correct energy carrier, be it district heating or cooling or electrical energy or compressed air or whatsoever, is produced using the optimal energy source.


Uu: Uprooting and under-vegetation

As a preparation for re-forestation, up-rooting is sometimes desired. This is also part of the normal rotation in orchards, vineyards and several other types of plantations. Stumps and roots, together with branches and other residues that should be removed and used for fuel will contain a significant part of the nutrients absorbed by the living trees and plants. Also an up-rooting operation will damage a significant part of the natural under-vegetation.

To restore and promote biological diversity and to maintain the productivity of the soil it therefore becomes necessary to re-circulate ashes from combustion plants to the sites from where the minerals and nutrients were withdrawn.


Vv: Versatile verifications

There are a large numbers of standards concerning not only how the quality of solid, liquid and gaseous fuels shall be determined but also for who has the responsibility to supply the quality certificate – the buyer or the seller.

To fulfil demands on sustainability, such certificates should also include the origin of the material. The presence and validity of such certificates and verifications will not only be important for the environmental credibility of the project but also be crucial to the end user, since fuel-fired plants are susceptible to variations in fuel quality.


Ww: World-wide perspective

Assume the world is a sphere, 40 000 km around.

Using school mathematics and assuming 30 % of the total area to be land, you will be able to figure out that the total land area is then about 150 000 000 km2. Divide that by the world population, 7 billion people, and you will find that each of us have access to a bit more than 21 000 m2 of land.

Of this land, about 6 000 m2 is infertile like deserts, high mountains and ice-covered etc. Another 6 000 m2 is forested. Almost 6 000 m2 is savannahs, steppes and such meagre land. Of the 3 000 m2 left, 2 000 are rich grassland. Only 1 000 m2 is well suited for agricultural production so that is where to grow food and to grow fibre for clothing.

Imagine making your living only from that and then make a choice if you want to grow dedicated energy crops on “your” agricultural land – or if you would prefer to grow edible crops.

In a sustainable energy system dedicated energy crops are banned unless they are part of a sustainable crop rotational scheme as green fertilizers, nitrogen fixation crops or alike.

This view of the world is the core of sustainable thinking.

Xx: XXL, xl, large or small?

A common misconception is to judge the size of biomass electricity production plants according to the scale used for coal and gas fired, condensing power plants.

The reason that coal power stations are XXL-sized is that they are typically situated in the middle of the open-pit coal mine and they are placed there without even considering the option to make use of the heat produced (about 60 % of the coal mined is converted to heat and only 40 % to electricity).

With gas used in combined-cycle plants, XXL or XL, the electricity produced may represent 60 % of the total input and losses thus “only” 40 %. With the costs for transport, such low efficiencies can never be accepted in biomass-fired plants but efficiencies higher than 90 % must always be strived for. This is achieved using CHP or tri-generation. The consequence is that biomass-fired plants become limited in size to what the local market for heating and cooling can accommodate.


Yy: Yield per year

Looking aside from the biomass produced in society, one could say that there are two major types of biomasses used for energy:

  • those that originate from annual crops and
  • those originating from perennial crops.

For planning purposes it is then important to remember that if the planning of fuel supply is based on the mean annual yield of annual crops, then that actually means that every second year there will be a shortage of fuel. To be on the safe side, one has to collect at the very least ten years of statistics, compute the mean yield and the standard deviation and then plan for a tonnage equal to the mean yield subtracted by one standard deviation.

For fuel based on perennial crops and forestry, the mean annual yield can be used – but not for annual crops.


Zz: Zealots and zanyism

Most anyone who has ever paid an electricity bill tend to feel competent to invent energy saving measures and energy generating devices. In some cases, such people can become so devoted to their ideas that they become a nuisance. Sometimes the suggestions can easily be discarded because they violate the laws of thermodynamics but remember that also Christopher Columbus was ridiculed, so do not dismiss them too easily.