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