Off-Grid Solar Lighting: Solutions, Savings, and Sustainability
Presented by: Newpathlight®
Baoan Qu, Shenzhen City,Guangdong Province, China
Provides an in-depth introduction into the technology and benefits of off-grid solar lighting. The course covers key considerations when selecting a system that is reliable, efficient, and cost-effective.
Purpose: Provides an in-depth introduction into the technology and benefits of off-grid solar lighting. The course covers key considerations when selecting a system that is reliable, efficient, and cost-effective.
Learning Objectives:
At the end of this program, participants will be able to:
• evaluate the environmental and economic benefits of off-grid solar lighting• discuss how the internal components of solar lighting work, including the solar panel,
charge controller, battery, and LED fixture• discuss the most important site factors to be considered when specifying an outdoor
solar lighting system: location, aesthetic requirements, operating profile, and lightintensity requirements
• explain how the components contribute to the overall system performance, longevity,and cost, and
• describe the advantages of off-grid solar lighting as shown by relevant case studies.
Solar is an ideal option when looking to lower electrical or installation costs, reduce the carbon footprint of a facility, diminish the impact to an environment, meet renewable mandates, or take advantage of renewable rebates.
Municipalities, military organizations, commercial properties, and national parks worldwide have benefited from a self-contained solar lighting system. This course will give an overview of how solar energy systems combined with long-lasting LED lights can provide a dependable, sustainable, cost-effective solution to a variety of lighting needs.
In 1876, William Grylls Adams and Richard Evans Day discovered that selenium produces electricity when exposed to light. The phenomenon is now known as the photovoltaic effect: light (photons) converted to electricity (voltage). This discovery was significant because it proved that a solid material could change light into electricity without the use of heat or moving parts.
In 1953, Bell Laboratories scientists were able to run electrical devices from solar energy for the first time, with the discovery that silicon can convert light into enough electricity to do so. The silicon solar cell was far more efficient than those made of selenium, but its high cost made it prohibitive for commercial markets.
The first major success for the silicon solar cell came when the technology was used to power both American and Soviet military satellites, and the increasing demand for solar energy in space led to its widespread use in non-military applications such as telecommunications satellites.
Solar technology was still too expensive for mainstream use until the 1970s, when lower cost manufacturing techniques were developed.
Commercially, solar lighting was initially used for remote applications where electricity was not available, such as off-shore oil rigs, lighthouses, and rural railway crossings.
Today, facility managers, homeowners, and municipalities are considering solar lighting as a viable option to meet their needs, no longer viewing it as an alternative source of energy, but often as the most effective solution.
Solar Myth #1
Solar lights are too expensive.
Fact:
The cost of solar has fallen significantly over the last few years, making solar a viable energy alternative.
When the costs of electrical infrastructure, trenching, and wiring are considered, off-grid solar lighting is a cost-effective alternative to on-grid lighting.
The environmental benefits of solar energy are now well-known. Solar energy is clean, renewable, and emission-free. In comparison, sourcing fossil fuels is an invasive process that causes geologic and ecological damage. Once excavated and transported, fossil fuels are burned to produce electricity, which emits huge amounts of greenhouse gas into the atmosphere; the byproducts of electricity generation can cause water and air pollution.
According to Carol Olson of the Energy
Solar Myth #2
Electricity is cheap and plentiful.
Fact:
When electricity was inexpensive and carbon was not a concern, we used wasteful lighting systems. It is time to rethink these out-of-date assumptions.
Research Center of the Netherlands, solar electricity compared to coal generated
electricity contributes 96‒98% less greenhouse gas, and over its lifetime: • uses 86‒89% less water• occupies or transforms over 80% less land, and• contributes 92‒97% less to acid rain and 97‒98% less to marine eutrophication (the
discharge of excess nutrients that can lead to algal blooms).
When it comes to a simple solar lighting installation, the environmental benefit is significant. A study of a parking lot in Colorado shows how solar lighting can result in 49% less CO2 production compared to a grid-connected system. • Over 20 years, this equals 89.8 fewer tonnes of CO2 released.• Equivalent to the CO2 emissions from 10,105 gallons of gasoline consumed
In addition to reducing carbon emissions, solar lights have the benefit of a low-impact installation process. Because a solar light does not have to be connected to an AC power source, there is no need for extensive construction. This makes solar lighting a responsible solution for parks, sacred lands, environmentally fragile areas, and other locations where minimal disruption to the natural environment is desirable.
Off-grid lighting installed on a trail through tribal wetlands on the Lummi Indian Reservation.
The low-impact design of off-grid solar lighting systems also has a direct result on installation costs. Solar lighting provides the following economic benefits: • Eliminates the cost of installing underground
wire, a distribution panel, and control panel.• Eliminates the cost of digging trenches for
underground wiring, including equipmentand crew costs.
• Eliminates the need for electrical meterinstallation and connection fees.
• Saves on the cost of replacing or repairinglandscaping that has been damaged duringinstallation.
• Eliminates the need to negotiate withproperty owners for underground rights.
Over the course of 10 years, the cost savings from eliminating associated electrical bills adds up significantly with an off-grid solar system.
With long-life, replaceable components, solar lighting can further reduce long-term operational and maintenance costs through the use of: • recyclable batteries (up to 5-year lifespan)• easy-to-clean panels (up to 20-year lifespan)• LED luminaires (up to 50,000 hours of operation), and• electronic components (up to 10-year lifespan).
When an energy facility in Mexico noticed that some of its parking lots were suffering from inadequate lighting due to old cables and long electrical lines, it knew it would be faced with challenges from stringent environmental protection mandates, limited on-site resources for lighting maintenance, and difficulty in receiving trenching permits because of its location near federal government property.
With no need to trench, solar lights allowed the facility to avoid time-consuming and costly permit procedures and saved the facility nearly $1.5 million in trenching and cabling costs alone.
In another example, when global security company Lockheed Martin needed to replace their existing 25-year-old streetlights for the main entrance roadway at their Florida facility, a cost analysis revealed that solar lighting would save $221,000 in initial and maintenance costs over 20 years.
Solar lighting also contributes to the building owner/developer bottom line by helping to meet renewable mandates, and may contribute to LEED certification points in categories such as:
• Sustainable Sites: Efficient LED optics reduce light pollutionand are a low-impact installation.
• Energy & Atmosphere: Both energy consumption and strainon the grid are reduced through on-site renewable energy.
• Innovation & Design: Off-grid solar lighting is an innovativesustainable building practice.
The three-story Brown Center for Innovation and Entrepreneurship at the Indian River State College (IRSC Main Campus in Fort Pierce was constructed to LEED Gold standards for green construction. The Center prepares students for cutting-edge careers in emerging technologies, particularly in energy related fields. IRSC needed a lighting solution for the prominent entry drive that would be in keeping with the sustainable purpose and construction of the facility; solar LED lighting met the lighting code as well as LEED requirements for the project.
Other Benefits of Off-Grid Solar Lighting: Ease of Implementation With a minimally intrusive installation process, off-grid solar lighting is also ideal for supplemental or portable lighting. • A facility may be powered by grid
lighting, but perhaps the originallighting layout creates unanticipateddark spots, so that additional lighting isrequired. Conversely, there may beareas where light must be relocatedbecause light trespass is creating anissue with neighboring property.
• When a property undergoes anexpansion, off-grid solar lighting canfill the need in the additional space or
Odessa College is a growing community campus with insufficient lighting between parking areas
and classrooms, and antiquated lighting and wiring from the existing system on campus.
light temporary parking areas in use during construction. • If existing underground wiring needs replacing or copper theft is a reoccurring issue, off-
grid solar lighting provides a security backup and autonomy from the grid when itspower is unavailable or unreachable.
Other Benefits of Off-Grid Solar Lighting: Ease of Implementation • No trenching or wiring required saves time
and cost.• Quick and easy installation is completed in
days instead of weeks.• No special equipment is required. Systems
can be installed with minimal tools andequipment. In some cases, a bucket truckmay be required.
• Existing work crews can be used. Manysolar lighting systems are pre-configured toconnect together and do not require anelectrician or approved contractor to install.A general contractor or facility andmaintenance crews can complete mostinstallations.
To build a solar lighting system that is reliable throughout the year and in all weather conditions, you need to ensure that the energy collected and stored in the batteries always exceeds the amount needed to run your light.
A complete solar lighting system is made up of the following: • Solar panel (PV)• Charge controller • Battery • LED driver and LED fixture
The photovoltaic (PV) solar panel, or module, collects and converts the sun’s energy into electricity. The PV panel is made up of individual silicon cells. When sunlight strikes the cells, it causes the electrons to move, creating a DC current flowing within each cell.
Different sizes (wattage) of solar panels are available and are carefully chosen based on site location, application, customer lighting requirements, and the amount of solar insolation (light) available.
Solar panels are durable and able to deliver reliable power even in extreme weather conditions.
Depending on the quality and materials used to create the cell, the capability and efficiency of a solar module varies.
Solar panel efficiency is the percentage of solar energy converted to electrical energy. The performance and capability of the entire system depends upon the energy collected from the panel.
The charge controller monitors and optimizes the power transferred to the battery. A battery’s charge capacity varies with extreme heat and extreme cold. A good charge controller ensures the battery stays topped-up but also protects it from damage due to overcharging and overheating. The charge controller additionally protects against accidental reverse polarity connections between the solar panel and batteries.
Different types of controllers can help you get more value out of your system under varying installation conditions.
Pulse Width Modifier (PWM) Controllers: This common controller technology is used satisfactorily in many applications. A PWM controller monitors the battery’s state-of-charge and simply lowers the charging current as the battery gets close to maximum capacity.
Maximum Power Point Tracking (MPPT) Controllers: Often a more expensive option, these controllers are ideal for challenging solar locations (for example: locations with long winters or frequent cloudy conditions). MPPT controllers allow you to have a high voltage panel paired with a lower voltage battery. This means your panel can collect the maximum amount of available solar energy. The MPPT controller receives the higher voltage and converts it to a lower one that the battery can tolerate without damage.
An energy management system (EMS) uses two integrated components: the charge controller and the LED driver.
The EMS in your lighting product ensures that the energy collected from the panel gets safely stored in the battery and efficiently delivered to the light fixture.
Sophisticated systems use EMS that are capable of managing dimming, and feature an LED driver to operate and regulate light output from the LEDs.
The electrical energy generated by the solar panel and managed by the controller is then stored in the batteries. This power is drawn from the battery to operate the LED luminaire from dusk to dawn. The size and amount of battery storage needed is dependent upon customer specified operating requirements and light intensities. When a supplier recommends a battery for your solar lighting product, they will be considering two important factors to ensure you get maximum value from your system.
Factor 1: How long can the battery last without charging?
It is important that sufficient battery storage is provided to operate each night and supply backup power in case of unexpected weather conditions. The amount of time a battery can last without charging is referred to as its autonomy. Typically, 3‒5 days of autonomy are required to ensure that your lighting system will continue to perform reliably.
Factor 2: How frequently will the battery need to be replaced?
A battery’s longevity will depend on how it is treated on a day-to-day basis. The amount of its capacity a battery expends each day is referred to as its daily depth of discharge or DOD. If the battery is lightly discharged each night (has a low DOD, less than 20% of its capacity used), it will last longer than if it is frequently “maxed out.” Similarly, the battery will last longer if it returns to full 100% charge each day.
By properly considering these factors, a supplier will recommend a battery that can supply your energy needs throughout the year and under all weather conditions while lasting for up to five years in the field.
Many solar battery technologies exist, including lithium, nickel metal hydride, and lead acid. The first two types can be very expensive and may not always be suited for outdoor solar lighting applications.
Lead acid battery types include absorbed glass mat (AGM), gel, and flooded—also known as wet cell. The most common battery for solar outdoor applications, in terms of commercial availability, price, low maintenance, and reliability, are AGM or gel types. These are leak-proof and designed to better manage a deep DOD, and typically last longer. Gel batteries have a similar lifespan to AGM batteries and can support a deeper DOD. AGM batteries can typically perform at wider temperature ranges.
The chart indicates typical lifespan of AGM and gel batteries in cycles. One cycle equals one discharge and one recharge of the battery (in the solar lighting world, typically one 24-hour period).
The graph additionally emphasizes the importance of keeping the depth of discharge to less than 20% of the overall total battery capacity—this keeps the number of cycles high and increases the overall product lifetime.
As previously mentioned, a battery will last longer if it is recharged to 100%. If only partial charging occurs, sulphate crystals form inside the battery and reduce its overall capacity. The more sulphation occurs, the more difficult it is to reverse this phenomenon.
Therefore, when a system is designed, it is critical to ensure that the batteries will be able to be completely recharged as often as possible. This dramatically 1. prolongs the service life of the battery, and2. reduces overall system maintenance costs.
Overcompensation due to poor weather conditions often leads to specifications of larger backup battery banks. Having too large a battery backup can actually be detrimental to the system and battery life, as the solar panels may not be large enough to completely recharge the battery bank.
Considering array-to-load ratio (ALR) helps ensure a battery is optimally sized.
ALR is the ratio of the power collected by the solar panels (or array) to the power spent by the light fixture (the load).
The amount collected by the solar array
should always exceed the amount spent
by the fixture.
Solar Myth #3
Solar lights do not last all night long.
Fact:
Improved solar illumination technology is reliable and, with adequate battery storage, will work through the night. Sophisticated solar lighting systems should provide 3‒5 days of autonomy.
The power collected by the solar array is calculated using insolation data. Insolation data is available from many sources such as NASA and NREL and measures the kWh/m2/day of solar energy available in various locations around the globe. Insolation data is often referred to as equivalent sun
hours or peak sun hours.
Map Credit: National Renewable Energy Laboratory for the U.S. Department of Energy. Billy J. Roberts. 19 September, 2012.
Insolation is not uniform across the planet’s surface. Even within relatively small regions, solar energy may vary greatly. For example, in areas around the Great Lakes, the available solar energy can be quite different from areas on one side of the region to the other.
Insolation also varies throughout the year. In the wintertime, the sun is above the horizon for fewer hours than in the summer. Also, even though the sun may be above the horizon for 14 hours a day, this may only result in 6 hours of equivalent full sun due to the angle of the sun and the amount of sunlight lost through the atmosphere.
ALR is typically calculated using the worst insolation month for an installation location. An optimal ALR to maximize battery life is typically 1.4:1, where the array delivers 1.4 times the power consumed at night by the load. A higher ALR allows the system to deal with inefficiencies, day-to-day weather variability, and panel degradation and dirt.
The lower the ALR, the higher the battery autonomy should be. A higher ALR means
battery autonomy can be lower.
ALR # of Days of
Autonomy
Batteries in Partial State
of Charge Result
1.1 : 1 10.46 14% of time Battery life will be severely shortened from undercharging
1.6 : 1 4.56 3% of time Batteries are well charged, reducing sulphation
• Storage: The battery bank should provide 3‒5 days of autonomy.
• Depth of Discharge (DOD): A battery will last longer with a low DOD, keeping thedepth of discharge to less than 20% of the overall total battery capacity.
• Battery Type: Lead acid is the most ideal type; AGM and gel are generally used.
• Partial State of Charge: A battery will last longer if it is recharged to 100%; avoidbattery banks that are too large and cannot be completely recharged by the solarengine.
• Array-to-Load-Ratio (ALR): The amount of solar collected should exceed the amountspent by the fixture (1.4:1 ratio).
The luminaire determines the amount of energy spent by the solar lighting system.
Solar lighting uses LED technology because of its low energy draw. LED technology can produce between 114‒210 lumens per watt compared to 80‒160 lumens per watt in high-pressure sodium (HPS lighting.
LED technology is continuing to advance so that more lighting can be produced with less power, reducing the cost for the same lighting output. LED luminaires are the most efficient lighting source available on the market at providing clear, high-quality light with more control options, reduced glare, and more effective lighting distributions.
Compared to HPS lighting, for instance, LED luminaires last for 50,000 hours or more, versus 20,000 hours for HPS.
Additionally, HPS shines light in a pattern directly beneath the luminaire, while LEDs can be configured to distribute light in a broader and more even pattern. A broader reach of light means that poles can be spaced further apart, reducing costs when fewer poles are needed.
LEDs have more flexible control options than traditional outdoor lights, so that they can be dimmed or controlled by motion sensors when vehicle or pedestrian traffic is low.
The best solar LED luminaires will be the same as those used in traditional on-grid LED lighting. This ensures that the standards defined by the Illuminating Engineering Society (IES) can be met without doubt. LED fixtures come in a wide variety of designs to suit architectural requirements and include a complete range of color temperatures and optical distributions.
However, a fixture must still be properly matched with the rest of the components in a solar lighting system. An effective LED lighting product is only as strong as its weakest link. Solar lighting suppliers will look to pair an appropriate fixture with the other components in the solar product to ensure maximum long-term performance and reliability of the entire system.
Spend Energy: Driving the Luminaire to Maximum Efficiency
The LED driver in the EMS is the last key component in your system. This will ensure that the output current from the system battery matches the current required to drive the fixture.
To make your system even more efficient, some advanced LED drivers can also establish custom operating profiles to minimize energy expenditure. This is ideal when a sufficiently dark sky allows the light to be seen at a lower intensity or when facility, pedestrian, or vehicular activity is reduced.
Before a solar lighting supplier can provide an efficient and cost-effective lighting system, several site factors need to be determined first by the architect, designer, or project manager: • Location• Aesthetic requirements• Operating profile• Light intensity requirements
Solar Myth #4
Solar lights don’t have as many options as a regular light.
Fact:
Solar lighting systems feature a number of the same options as grid-tied systems. The most popular include dimming, decorative poles and fixtures, and multi-fixture design.
When designing a solar lighting system, solar panels are selected and sized to balance a number of end user requirements. As mentioned previously, the amount collected by the solar array should always exceed the amount spent by the fixture.
Generally, as long as there is sunlight, a solar panel will generate some amount of power. Locations that have lower insolation can still have viable solar lighting with proper system design.
The solar insolation map at right shows the average solar collection per day , based on the insolation values for the worst month of the year for a given location. Solar lighting suppliers can help determine your location’s solar insolation value to help chose the correct lighting system.
Even in extreme heat and cold climates, solar can be a viable solution for outdoor lighting when systems use components designed for tough environments. In latitudes that receive snow, panels are normally angled at 45 degrees or more for maximum solar collection. This also prevents snow build-up from inhibiting energy generation. Solar outdoor lighting systems are also designed to withstand high winds, hail, humidity, and salt, and are individually grounded to protect from lightning strike damage.
Shading
A clean panel ensures maximum capacity for electricity generation, and the area of installation should be clear of obstructions and shading from buildings and trees.
High-efficiency solar panels combined with an efficient EMS and battery bank can capture, store, and power a light with a smaller surface area. Small, efficient panels are an appropriate choice for pedestrian areas and parks.
A good solar supplier will be able to design a system to collect sufficient energy while keeping the overall physical size in check.
Some lighting applications require the use of decorative poles or fixtures to match a neighborhood theme. Solar lighting systems can be installed on most pole designs. Additionally, many decorative LED fixtures can be adapted to work with solar-powered systems.
Two Fixtures on a Pole
In some lighting designs, two fixtures are required to be mounted on the same pole. This option is possible with solar-powered systems as well. However, increased lighting levels need to be accounted for when sizing the solar panel and battery to ensure adequate energy collection and storage capacity.
An operating profile determines how and when the light should be applied for the most efficient and effective use of available energy. It allows for the light to be dimmed or turned off completely when facility, pedestrian, or vehicular activity is reduced. This saves energy consumption, and reduces the amount of energy required to be stored and overall system size.
For example, a typical split night operating profile has your fixture turn on at dusk at 100% for a fixed number of hours, then dim to a lower percentage in the middle of the night before returning to 100% as the sun rises.
Example of Split Night Profile Light dims during times when application usage is less
Many solar outdoor lighting systems are designed to meet IES lighting level and design standards, local and International Building Code standards, and zoning bylaws
The components of a solar lighting system may at first seem complex; however, a good solutions provider will help to ensure that all pieces of the puzzle come together seamlessly.
A supplier will design a system by simply tweaking the major components and by integrating a quality EMS to produce the most efficient, long-lasting, and cost-effective lighting solution.
As with traditional outdoor lighting fixtures, there are a number of services a good supplier should offer: • Photometric study• System drawings• System specifications• Pole sizing information• Modeling tools specific to solar lighting
Modeling tools will simulate the environmental conditions and product performance for the exact installation and application, evaluating not just how the solar panel functions in your region of the world, but also how the entire system will interact and perform under the conditions in your exact location through all four seasons.
A good modeling tool can take into consideration even minor factors such as the angle that the system panels face the sun. For best efficiency and performance, system modeling tools should optimize tilt angle based on the geographic location of the installation—regions further away from the equator will need a greater degree of tilt for optimal energy collection.
Look for a manufacturer who will use these tools to provide you with maximum light output, maximum autonomy, and maximum reliability based on exactly where and how the light will be used. The next section illustrates some examples of these principles put into practice.
Dockside Green aims to develop an eco-friendly community that offers true environmental sustainability. the goal is for the master-planned community to obtain Platinum certification for all its buildings.
The community is designed to encourage walking, running, and cycling, so effective lighting and safety-enhancing technology along its trail is essential. Solar lighting provides a versatile and reliable illumination alternative that is eligible for LEED credits and can help Dockside Green in its commitment to developing a LEED Platinum community.
FranceThe Spokane Public Facilities District (SPFD) has adopted a sustainability policy for all its venues, mandating that they be operated in an environmentally friendly manner. Therefore, solar lighting was top of mind when lighting alternatives were sought for a new parking lot next to the showcase performing arts center.
Besides the demand for a renewable energy source, the lighting also needed to dependably meet the high light output standards required for parking lot safety. Portability was also a requirement, as the SPFD wanted a long-term solution that could be moved and placed in a different location as site size and requirements changed.
The dark sky-friendly lights help reduce the city’s light pollution. The solar-powered technology and 50,000-hour LED lifespan significantly reduces maintenance costs and will eliminate electricity costs altogether. The lighting design gives the SPFD the opportunity to emphasize their commitment to green practices while providing safe access in a popular area.
IndonesiaSolar lighting met an immediate need for temporary barracks parking lots after September 11, 2015. Solar lights and direct burial fiberglass poles were ordered in August 2015 for installation along a pathway. Security requirements after September 11th required vehicle parking to be moved away from all buildings, including barracks. Temporary parking areas were built next to the barracks, and the solar lights were able to be installed immediately without being connected in any way to the power grid.
Analysis of roadways on the Lummi Nation Reservation revealed that Haxton Way had the highest rate of fatalities. Only a ditch or a few inches of asphalt were available for pedestrians, who used the route frequently to get to stores and work. A pedestrian path was built in response to the obvious and urgent safety concerns.
In considering lighting options for the path, safety and cost were issues, as well as the fact that the pathway goes through wetlands whose preservation is very important to the Lummi Tribe. Off-grid solar powered LED lighting met all the demands.
Haxton Way Pedestrian Path, Lummi Nation, Washington
Residents feel the benefits of improved safety not only in getting to work or shopping, but in overall health, as the path provides a safe exercise route. The lights are motion activated to brighten to 100% as a pedestrian or cyclist approaches, and then return to 25% brightness. The lower right photo shows the bridge portion of the pathway that passes through the tribal wetlands; because the lighting required no trenches or drainage in order to be installed, the project’s environmental impact is kept to a minimum.
The Colorado town of Wray is situated on the Republican River and is known for its rich opportunities for springtime bird-watching. A trail that meanders along the river and through town for two miles presented some unique lighting challenges.
The presence of groundwater along the trail made the choice of off-grid lighting an obvious one. Because no trenching or wiring was required, the project saved money and made minimal impact on bird habitats.
