EECo.Environmental
Low Energy and Renewables
Qu: Why are we choosing low energy systems and more environmentally benign technologies ?
Ans: To improve quality of all our (Global) lives.
The following are some examples of death and general lowering of the quality of life due to energy and industrial related activities, they only quantify the effects on human life :
The more insidious effects of pollution, as already said, are difficult to identify and connect to environmental degradation. However, the occupational health risk to coal miners contracting the respiratory disease, pneumoconiosis, identifies the unseen dangers of poor air quality, in the UK around 300 deaths per year are attributed to pneumoconiosis.
Other examples are difficult to find and due to long term predictability problems are only estimates, however, conservative investigations have found that annual deaths in the UK directly attributable to atmospheric emissions from coal/oil fired power stations and urban transport could amount to around 200 respiratory disease deaths per year and 1000 cancer deaths per year.
In comparison with major accidents, these deaths are dispersed and continuous and so do not make the media headlines. They do however represent a significant risk to the publics health, perhaps a higher risk than one of the most common fears among people, that of pedestrian motor traffic accident. Pedestrian road traffic accidents account for only 1000 deaths per year for people aged between 5 and 60.
The risk to our health and quality of life, mainly due to respiratory disease and cancer ultimately leads to death but, it is also disabling throughout life as with asthma sufferers. Asthma among children and newly developed asthma is on the increase in the UK,................ . (Ongoing Mphil research by Mark Anderson of EECo. Environmental)
Application Suggested Unit size per kW Connection/Storage Uses and Disadvantages
small scale output power required Advantages
energy
capacity
Solar (Photovoltaic) 10W to 10kW 13m2 at STC Array mounting, Electricity High capital
(1000W/m2 solar Charge production, No cost, Requires
irradiance) controller, fuel required, No storage for 24hr
Battery storage, Pollution, Long use, Training and
DC/AC inverter, Life (20yrs), High infrastructure
Switchgear reliability, Very needs,
low maintenance, Performance is
No supervision, weather
Low running cost. dependent, Large
area requirement.
Solar (heating) 1kW to 10kW 2m2 Flat plate Panel Mounting, Water heating, Requires storage,
collector at STC Pipework, pumping Timber/crop climate
(average (optional), drying, Cooking, dependent,
efficiency of Insulated Distillation/desali Maintenance
50%, temperature storage, nation, Low/zero training,
increase from 20 Temperature energy input, Freezing,
to 60oC) control. Low/zero Thermosyphon air
pollution, low locking/back
maintenance, low syphoning.
cost
Application Suggested Unit size per kW Connection/Storage Uses and Disadvantages
small scale output power required Advantages
energy
capacity
Wind turbines (power gen') 50W to 100kW 7m diameter Foundation, Proven technology, Wind speed
Turbines blades at average switchgear and Automatic dependent, Siting
annual wind speed distribution operation, No restrictions,
of 5m/s cable, fuel, No High capital
storage/inverters. pollution, Long cost,
life (15 years), Construction
Sectional restrictions,
manufacture. Visually
obtrusive, Some
storage required,
Back-up system
required,
Technically
intensive
installation.
Wind turbines (pumping) 10W to 100kW 10m dia blades at Foundation, bore Proven technology, Wind speed
Turbines 5m/s wind speed, hole, pump, Automatic dependent, Siting
will lift 37m3/h extraction operation, No restrictions,
of water through pipework, storage fuel, No High capital
10m. vessel, pollution, Long cost,
filtration, life (15 years), Construction
distribution Sectional restrictions,
pipework. manufacture. Visually
obtrusive, Some
storage required,
Back-up system
required,
Technically
intensive
installation.
Application Suggested Unit size per kW Connection/Storage Uses and Disadvantages
small scale output power required Advantages
energy
capacity
Water turbines (power) 1kW to 100kW 0.02m3/s (20kg/s) Weir, reservoir, Fairly constant Site
flow rate for10m pipework, turbine power suitability/proxim
head. and housing, availability, easy ity to resource,
generator, waste technology, No power output
pipework, fuel, low fixed to water
controls and maintenance, Long resource, Dry
cabling. life (20yrs), Can season
be low cost, No vulnerability,
large scale Moderate skills
damming/civils, No needed, Can be
pollution. high cost.
Geothermal (heat & power) 100W to 100kW Earth surface Geological Fish hatcheries, Expensive
mean heat flux survey, bore hole soil warming, drilling, danger
(60mW/m2) = drilling, Heat space heating and of eruptions, Not
16,000m2 per kW. transfer or fluid cooling (heat always renewable,
Surface Hot Spot transfer pumps), drying, Atmospheric and
heat flux pipework, bathing, waste pollutants,
(300mW/m2) = Filtration, refrigeration land use for
3,333m2 per kW. Effluent disposal (absorption), lagoons.
Bore holes to (direct use only power generation
depths of upto e.g. power (large scale steam
1000m (upto plants), End use turbines),
100bar pressure) technology.
release
temperatures from
30oC to 200oC.
Application Suggested Unit size per kW Connection/Storage Uses and Disadvantages
small scale output power required Advantages
energy
capacity
Biomass (heat and power) 5kW to 300kW 1.25kg of Civil work Renewable, solid, Land use, low
gasified dry preparation, gaseous or liquid, energy density,
biomass will Storage of scale is broad, water and
produce 1kW of biomass, Indiginous fuels fertilisers
electicity plus Gasifier, and technology, required, Complex
1.75kW heat seperator, Zero atmospheric management
filter, pollution systems, Bulk
condensate addition, creates transportation,
collector, jobs, Residue Pest/weather
filter, modified usage and vulnerability,
riciprocating financial benefit. Technical and
engine and resource
generator, variability,
switchgear/control Residue handling.
s, distribution
cable and
pipework.
How do we begin to estimate the capacity ?
Wind Data
Location Annual mean % Estimate Notes
Wind Speed of annual
(m/s) hours of
frequency
Iceland(65oN) >7m/s 70% Gusts, turbulence
Tazmania(42oS) >7m/s 60% Gusts, turbulence
Western n/a n/a only very small
Samoa(15oS) scale
Oman(20oN-25oN) <5m/s 30% marginal site,
large diurnal
swing
2. Estimating the power output:
a). Wind Pumping
Average hydraulic power P = 0.1 x A x V^3
Estimating how much water will be pumped Q = P/9810 x H
b) Wind Electicity
Average electrical power P = 0.2 x A x V^3
Solar Data
Location Tilt angle Mean Daily hours of Notes
and 24hour collection for
orientation clr/cldy 'x' months per
of device solar year
irradiance
(W/m2)
Iceland(65oN) 65o , 180 9 hrs/day, 8 Summer use
South mth/yr only, remote
sites &
holiday homes,
sensitive to
horizon
landscape,
fixed
orientation is
limiting.
Tazmania(42oS) 42o , 199 9 hrs/day, Remote sites &
North 10mth/yr holiday homes,
sensitive to
horizon
landscape,
fixed
orientation is
limiting.
Western 15o , 380 12 hrs/day, ideal
Samoa(15oS) North 12mth/yr situation,
(taken as
horizontal)
Oman(20oN-25oN) 22o , 360 12 hrs/day, ideal
South 12mth/yr situation,
(taken as
horizontal)
2. Estimating the output:
Photovoltaics -
a). First find your power requirement - E (Watt hours per day),
b). Find the load on your array L - = E/(battery x regulator efficiency),
(NB. - 0.8 and 0.9)
c). Find the daily irradiance I (Wh/m^2/day) - = Irradiance x hours/day,
d). Find the array capacity (Watts) - = L/I
e). Find the battery storage size (Amp hours) - = E/(max battery discharge x Voltage)
(NB. - 0.2 and 12)
Note: for 240Volt equipment supply an inverter is required after the battery storage system with an efficiency of around 85%.
a). Using the rule of thumb given for flate plate collectors of 1kW output for a 2m^2 at STC raising water from 20oC to 60oC, the water flow rate would be around 6 litres/s.
b). For solar irradiance other than STC the output of the flate plate collector will be proportionally less.
e.g. Oman - from above tables 360W/m^2 , 360/1000 = 0.36,
therefore only 2.16 l/s would be heated.
Daily heating is simply 2.16 x hours heating per day (from above table)
i.e. 2.16 x 12 = around 26 litres per day at 60oC from 2m2 panel.
a). Using the rule of thumb given in tables, for 1kW of electricity 20 litre/s of water falling through 10m is required. This could be delivered by a pipe system running down a hillside where the vertical distance it descends is 10m. The pipe diameter would be around 150mm (6 inches). Note: this rule of thumb accounts for all efficiencies of electrical generation.
b). Doubling the head to 20m halves the amount of water required for the same amount of power (1kW) and will almost halve the pipe diameter. A general rule of thumb for pipe diameters in this application is a reduction or increase by 1/3 for a halving or doubling of volume flow rate.
e.g. Tazmania - For a lake, stream/river or water fall 100metre above the location of the turbine, a 10kW electrical demand will be satisfied by 20 litres/s (0.02m3/s):
Power output (P) = V x H x 5 Where:
V = m^3/s flow rate
H = metres head
Note: Most small scale turbines can be operated in reverse acting as pumps, good option for storage, when working with other forms of electrical generation.
