Solar & SmartIs there a place for solar in the “Smart City”?
Chris Angell C.Eng. MIET Pudsey Diamond Engineering Ltd
Everyone Knows a bit About Solar……• Your garden lights look great for an hour or two…..in
summer• That solar-powered floodlight on the garage, is ok but it
could be brighter• Remember the solar-powered calculator which needed
more light than you needed to see by or it couldn’t add up?• Do we have enough sunlight in winter to operate
anything useful?• Solar powered devices are autonomous aren’t they? They
don’t need maintenance!!!
This presentation seeks to address these issues and show how, with
careful consideration of all the factors, it is possible to power modern devices, by solar power alone
As cities become smarter, solar will emerge as a very smart choice
The Case For Solar• Small solar panels are inexpensive, and batteries are easy to
charge from them• Solar panels have a long life (typically 20 to 25 years)• Apart from occasionally wiping them if they get dirty, they are zero
maintenance energy gatherers• While in countries like the UK the number of sunshine hours is
often limited, the annual average insolation (solar radiation that reaches the earth's surface. It is measured by the amount of solar energy received per square centimetre per minute) is significant• As long as enough energy storage is provided to store energy
whenever it is available, solar can be made to work reliably throughout the year
Existing Technologies• Many simple solar powered systems are designed
(primarily for cost reasons) to operate well in the summer (when energy is abundant) and not so well in the winter• In lighting systems this means operating for a few hours each
day but not all night
• This is dubious for lighting and totally unacceptable for other applications• The energy demand from the solar powered device must
be reduced by smart engineering to reduce the solar panel size and the storage battery size• Until recently, solar powered lighting systems did not
have energy to spare and were not connected to a data network
Reliability• In the context of solar energy, reliability really
means energy availability• If the solar panel is too small, insufficient energy will be
harvested to charge the battery system• If the battery system is too small there will be insufficient
energy stored to reliably operate the device, and some solar energy will be wasted• In either case the result will be an unreliable unit
The Harvester/Storage Balance• As days lengthen and shorten with the seasons, the
amount of solar energy available changes too• In many cases the demand alters with the seasons
too, and not in a good way!• If solar energy is being used to provide lighting of any
kind, winter provides the greatest solar challenge – short days, low angle of sun, long nights, bad weather – it all conspires against solar harvesting
• Summer offers a bumper harvest but we mustn’t waste it, so determining the capacity of batteries and panels is crucial
The Annual Averages• Energy harvested throughout the year must match
the demand
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec0
2
4
6
8
10
12
14
16
18
UK Insolation KWh/m2 and number of night hours(source: "The Eco Experts")
London SE Eng NW Eng Night Hours
Achieving Balance1. Careful calculation and design can ensure that sufficient
energy is gathered during the summer months (when energy demand for anything illuminated is at its lowest, and solar energy availability is at its highest) to cover the energy shortfall during the winter
2. Factors such as total expected insolation (solar radiation from the sun), battery capacity, total annual demand must all be used to design a robust system• The key here is to think “annually” not just day by day
3. Battery efficiency can be easily overlooked, so an additional factor to compensate for this must be included (as a rule of thumb the total energy captured should be 1.33 times the actual requirement, to overcome battery inefficiency)
Coming of Age for Solar• While solar cells and panels themselves have not
fundamentally changed significantly for several years (except for their cost which has fallen dramatically) systems powered by them have:• Modern electronics allows for the design of very
low power devices • LEDs have dramatically reduced lighting power
consumption• Part-night lighting has changed the energy balance
making solar easier to employ
Coming of Age for Solar• Battery storage systems have become more sophisticated
• Though Lead Acid systems still have their place – there is no cheaper chemistry, they can be easily re-cycled and with care they can perform well against their more expensive “younger brothers” such as Li ion
• Even wireless (RF) devices are more efficient today and can be easily shut down when they are not needed• In fact for telemetry systems, operating licence free, there is a
requirement that they operate at a 1% duty cycle (for transmission) meaning that for 99% of the time they are only receiving which certainly helps to drive energy consumption down
• So although solar panel efficiencies have not increased greatly in recent years (14% - 16%), progress in other areas has increased the usefulness of solar as an energy source
What is Smart in Smart Cities?• Smart begins with simple control from a remote location
• Turning street lights on and off• Possibly dimming of streetlights• Generally used for managing the reduction of energy usage
• This evolves towards improving maintenance• Data returned from assets about current health (does the
lamp need replacing?)• Is the asset dirty (requires cleaning)
• Which needs a two-way communication system• With “intelligent” devices to manage the communication and
asset’s internal sensors• …and interfacing with CMS
But It’s Not Just About Lighting• The “Smart” in Smart Cities is about gathering data and
using it to improve the city experience for drivers and pedestrians• Real-time adjustment of traffic flow (through the use of
dynamic signs)• Because of congestion• Poor air quality• Road Traffic Incident• …..
• Road level temperature measurement to target the use of gritting in the most efficient manner or to provide ice warnings to drivers
Direct Information To Your Phone• After data analysis, some information could be made
available to phone users through “Smart City Apps”• Data will be returned to the city via local Wi-Fi
hotspots, or the use of visible light communications (Li-Fi – Light Fidelity)• In-car this can be used to inform the driver of road
closures or congestion or could direct the driver to nearby available parking (in the near future this will include the availability of car charging points for electric cars)
Information, Information, Information• Smart Cities will be thirsty for data
• To make useful decisions about deployment of resources• To allow detailed traffic analysis• To offer predictions about air pollution build up and
movement• To provide a view of congestion build up, real time,
offering the possibility of re-directing traffic before a log-jam occurs• There will be other uses for data, currently unforeseen –
the more data that is available the more analysis that can be done
Sensors Where They Are Needed(not just where they can be powered)• At road level (street temperature for gritting
decisions)• At human height (air quality sensors)• At the side of the road• On traffic islands• Even out of urban and suburban areas• But providing power to sensors where they are
needed could be very expensive and inevitably compromises will be made
Sensors Where They Are Needed• Solar powered devices make this possible:• No mains wiring• No closing and digging up the road• Just enough light and a wireless interface• Put them wherever they are needed
Sensors On a Traffic Island
Solar energy
One current
example is a traffic bollard
Powered by solar,
illuminated at night by
LEDs
It also monitors
road temperature
…
Temperature
…and ambient
light level…
And makes the
information available wirelessly
Light level
Getting Data to the Office• A quick thought on how data is brought back• CMS – a general term for control and management –
itself will depend on:• Open interface(s) – to ensure that all sorts of data can
be gathered from analysis• Standards – can be seen from two perspectives
• standards undermine “proprietary” systems where a customer is “locked in”
• BUT offer a wider support for peripherals and opportunities for manufacturers to introduce their own USP – the mobile phone is a prime example of this – standards allow phones to work everywhere
Solar is Smart• Devices powered from solar energy can be deployed almost
anywhere• After initial outlay they cost almost nothing to run• Low power solar powered two-way communication allows
measurement, control and data gathering anywhere• Now a solar powered lighting system can monitor itself and
alert maintenance crews making their work much more efficient• Smart can go beyond dimming street lights:
• Sending out gritting trucks only when they are needed is economically smart and saves energy
• Dynamically controlling traffic flow reduces congestion, improves air quality and increases productivity – ultimately saving energy in a very smart way
• Actively monitoring and controlling ambient light levels instead of controlling by consumed power
So, is there a place for solar in the “Smart City”?• Clearly solar powered devices can contribute enormously to
the provision of data into the Smart City realm• Solar is “Smarter” in the broader sense than other
technologies because it is already an energy efficient technology• With the cost of providing mains power to ideal sensor
locations sometimes prohibitively high, solar is often the only solution• Solar powered devices can communicate successfully into
the Smart City Network, they can be reliable and they are inexpensive to run• The answer must be: “YES THERE IS!”
Chris AngellPudsey Diamond Engineering Ltd
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