If the only difference between 60- and 72-cell solar panels is their size, how do you choose one over the other?The ultimate decider is panel value, measured in cost-per-watt.Divide the price of the panel by the rated panel output (typically 250W-375W per panel). This will give you a baseline to compare panel value, regardless of size.Our advice is to go for the best cost-per-watt option that fits the space where you will install your system.Here’s an example. If your mounting space is 35’ wide and 10’ tall, you can only fit a row of 10 panels. You can install more power by using 72-cell panels because you have enough space to accommodate the taller panel size.
1. Cycle lifeWhen you discharge a battery (use it to power your appliances), then charge it back up with your panels, that is referred to as one charge cycle. We measure the lifespan of batteries not in terms of years, but rather how many cycles they can handle before they expire.Think of it like putting mileage on a car. When you evaluate the condition of a used car, mileage matters a lot more than the year it was produced.Same goes for batteries and the number of times they’ve been cycled. A sealed lead-acid battery at a vacation home may go through 100 cycles in 4 years, whereas the same battery might go through 300+ cycles in one year at a full-time residence. The one that has gone through 100 cycles is in much better shape.Cycle life is also a function of depth of discharge (how much capacity you use before recharging a battery). Deeper discharges put more stress on the battery, which shortens its cycle life.2. Depth of DischargeDischarge depth refers to how much overall capacity is used before recharging the battery. For example, if you use a quarter of your battery’s capacity, the depth of discharge would be 25%.Batteries don’t discharge fully when you use them. Instead, they have a recommended depth of discharge: how much can be used before they should be refilled.Lead-acid batteries should only be run to 50% depth of discharge. Beyond that point, you risk negatively affecting their lifespan.In contrast, lithium batteries can handle deep discharges of 80% or more. This essentially means they feature a higher usable capacity.3. EfficiencyLithium batteries are more efficient. This means that more of your solar power is stored and used.As an example, lead acid batteries are only 80-85% efficient depending on the model and condition. That means if you have 1,000 watts of solar coming into the batteries, there are only 800-850 watts available after the charging and discharging process.Lithium batteries are more than 95% efficient. In the same example, you’d have over 950 watts of power available.Higher efficiency means your batteries charge faster. Depending on the configuration of your system, it could also mean you buying fewer solar panels, less battery capacity and a smaller backup generator.4. Charge RateWith higher efficiency also comes a faster rate of charge for lithium batteries. They can handle a higher amperage from the charger, which means they can be refilled much faster than lead-acid.We express charge rate as a fraction, such as C/5, where C = the capacity of the battery in amp hours (Ah). So a 430 Ah battery charging at a rate of C/5 would receive 86 charging amps (430/5).Lead-acid batteries are limited in how much charge current they can handle, mainly because they will overheat if you charge them too quickly. In addition, the charge rate gets significantly slower as you approach full capacity.Lead acid batteries can charge around C/5 during the bulk phase (up to 85% capacity). After that, the battery charger automatically slows down to top off the batteries. This means lead acid batteries take longer to charge, in some cases more than 2x as long as a Lithium alternative.5. Energy DensityThe lead-acid batteries featured in the comparison above both weigh around 125 pounds. The lithium battery checks in at 192 pounds.Most installers can handle the extra weight, but DIYers might find the lithium batteries more challenging to install. It’s wise to enlist some help lifting and moving them into place.But that comes with a tradeoff: the energy density of lithium batteries is much higher than lead-acid, meaning they fit more storage capacity into less space.As you can see in the example, it takes two lithium batteries to power a 5.13 kW system, but you’d need 8 lead-acid batteries to do the same job. When you take the size of the entire battery bank into account, lithium weighs less than half as much.This can be a real benefit if you need to get creative with how you mount your battery bank. If you are hanging an enclosure on the wall or hiding it in a closet, the improved energy density helps your lithium battery bank fit into tighter spaces.
As we have already hinted, the main principle of how solar lighting works is very simple. These lights collect solar energy and transform it into lighting—through a technology called the photovoltaic effect which is used in a solar panel. This effect collects solar energy. throughout the day and stores it in a rechargeable lithium ion battery that can be used later in the evening when there is no sunlight.Solar LED lights can be installed in many different areas. They offer amazing environmental benefits and can burnish a building owner’s green credentials, serve as a unique selling point for attracting and retaining tenants and help buildings or retrofits to quality as LEED points.
Us Energy storage provider Powin Energy, engineering and project management vendor Sungrid and a subsidiary of customer Kruger Energy have announced they are working together to deploy a 2MWh Energy storage project. The project will reduce peak power demand from utilities by users in Ontario, Canada, and the use of battery storage systems is a huge opportunity to reduce power costs and reduce carbon emissions.The battery storage system is being deployed by Kruger at its Brampton packaging plant, which produces containers for food, beverages, chemicals, textiles and many other products and industries. Cyrus Etemadi, Energy Storage Manager at Kruger Energy, says: "During the current coronavirus outbreak, our Brampton plant is operating 24/7, so there is much more to be gained from deploying and running the Energy storage system."Ontario's Global Adjusted Cost (GAC) policy is being implemented by independent power System Operators (IESO) that operate the grid and remains a major source of revenue for grid infrastructure and clean energy. Over the past few years, Canada has invested tens of millions of dollars to deploy energy storage projects of various sizes. Powin Energy says it has deployed more than 100MW of Energy storage and plans to deploy about 80MW.Kruger said that while its recent deployment of energy storage projects was small in overall terms, it was the company's first pilot project in energy storage and received a large number of RFPS from key bidders with expertise in energy storage technology."We have done extensive research with SunGrid and Powin Energy on Energy storage deployment, with a particular focus on the safety of battery Energy storage systems," Etemadi said. Ultimately, they came up with a lithium iron phosphate battery energy storage system that is safe, reliable, has a long working life, is environmentally friendly and non-toxic, and does not use cobalt."Other energy storage projects in Ontario that have been deployed include an 8.9MW/18MWh battery energy storage system by Fortune 100 technology company Honeywell, which was deployed last May; Shell's industrial customers in Ontario are deploying a battery storage system through a partnership with Energy storage developer Convergent Energy + Power. Earlier this year, private-equity investor Blackstone Energy Partners bought Toronto-based NRStor C&I, a former subsidiary of Canadian energy-storage developer NRStor.Jeremy Goertz, general manager of SunGrid Solutions, said: "In Ontario, large load users pay about 70 per cent of their electricity bills during peak demand (about five hours). This situation provides users with the opportunity to deploy battery storage systems to reduce power demand during peak periods."
The energy storage of a battery can be divided into three sections known as the available energy that can instantly be retrieved, the empty zone that can be refilled, and the unusable part, or rock content, that has become inactive as part of use and aging. As the rock content portion of the battery grows, the charge time shortens because there is less to fill. Quicker charging times on faded batteries are noticeable especially with nickel-based batteries and in part also with lead acid, but not necessarily with Li-ion. Lower charge transfer capability that inhibits the flow of free electrons prolongs the charge time with aged Li-ion. In most cases, the decrease is linear and capacity fade is mostly a function of cycle count and age. A deep discharge stresses the battery more than a partial discharge. It is therefore better not to discharge the battery fully but charge it more often. A periodic full discharge is only recommended on nickel-based batteries to control “memory” and on smart batteries as part of calibration. Lithium- and nickel-based batteries deliver between 300 and 500 full discharge/charge cycles before the capacity drops below 80 percent.Specifications of a device are always based on a new battery. This is only a snapshot, which cannot be maintained over any length of time. As with any shiny new machine, the battery will fade and if left unchecked, the reduced runtime can lead to battery-related breakdowns.A pack should be replaced when the capacity drops to 80 percent; however, the end-of-life threshold can vary according to application, user preference and company policy. Capacity measurement, a service that remains the best indicator for replacement, should be done every 3 months with active fleet batteries.Besides age-related losses, sulfation and grid corrosion are the main killers of lead acid batteries. Sulfation is a thin layer that forms on the negative cell plate if the battery is allowed to dwell in a low state-of-charge. If caught in time, an equalizing charge can reverse the condition. Grid corrosion can be reduced with careful charging and optimization of the float charge.With nickel-based batteries, the rock content is often the result of crystalline formation, also known as “memory.” A full discharge/charge cycle often restores the battery to full service. A periodic full discharge while the battery is in service keeps the crystallization under control and prevents damage to the separator.