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Energy Storage in Batteries

If a Solar Retailer tells you Batteries are currently to expensive & takes too long to break even on your investment. Walk away from these people & shop around !

The main reasons behind that statment is either there profit margin are high, or commonly you will find most Solar Retailers push to sell you an over-sized Solar system, as there main focus is to get You to sign over your 12 years of "Small-scale Technology Certificates" (STC), for a 6kW array equates to *$3'300~$4'500, Not bad profit for what should only take a Day to install 20 rooftop solar panels!

Thankfully Retailers are slowly being replaced by online businesses like ours, and contract electrical installers that commonly don't have the fancy overheads & trappings of a conventional shop-front business, so you will save !

How does Energy Storage work ?

Energy produce via Solar, Wind or Aqua generation is first sent into a Hybrid inverter, where the inverter first provides energy to your premises, then any excess energy is first sent to charge your Batteries, via Battery Management System (BMS), and then any excess/waste energy can be sold via a P2P Energy Trading platform, or exported as a Feed-in Tarrif to your energy retailer.

Commonly charged batteries sit idle ready for sunset, where the stored energy is then used to power your premises until Sunrise.

Battery storage systems all have different size footprint, capacity, efficiency and cost per kWh, the best battery systems will provide good value for money and last many years past there guarantee period and cycle life, allowing you benefit long after passing the investment break-even point, from there onwards it will be all savings!

What size battery is require to become Energy Independent or go Off-grid ?

This is largely dictated by your Daily energy consumption, and how you want to black-out proof your premises!

Example: If your premises consumes 15kW of energy/power per 24hr day, and 5kWh between sunset to sunrise, then a 5kWh battery would be the ideal starting point, where a 15kWh battery will provides power security for 24 hours or greatly assist during sustained bad weather.  Additional energy can always be generated using a small cheap Gen-set to totally black-out proof your premises, if that is your goal.

No matter what battery storage system you purchase, you should Calculate the following;

  1. The Battery cost per kW: The less you pay for quality batteries the quicker the break-even into profit period is accomplished.
  2. Battery Life: Is calculated using the manufacturers energy Throughput or Cycle life figures;
    1. Throughput: If the manufactures energy Throughput is 55'000kWh ÷ 15kWh battery = 3'666 days = 10 years.
    2. Cycle Life: If the manufactures Cycle life is 3'500 times ÷ 365 = 9.6 years.

NOTE: There is a New Commercial Thermal Energy Storage Technology (1414° TESS unit), the directors of this company have stated "it will be 1/10th the cost of large Commercial Energy Storage solutions like TESLA". This system would be very suitable for storing energy spillage, what would be normally wastes energy, and be very suitable for Community Energy!

If you already have Solar: You are way ahead of the rest, as your break-even point to re-coup your Battery investment, will commonly be between 1~3 years !

So, remember when investigating in a micro grid, you need to purchase a Hybrid Bi-directional inverter (not a solar inverter), Hybrid inverters are compatible with variable input voltages, and cost from $900~$3'000 depending on the brand and kW rating, if you intend to operate 3 phase power, you can purchase single 3 phase inverter or three separate single phase inverters, depending on what you are trying to accomplish.

Lithium-Iron phosphate (LiFePO4) batteries offer lowest cost & energy density per kW, and have longer lives and less likelihood of failure from fire & explosion. Such batteries are widely used in electric tools, medical equipment, and other roles.  LiFePo4 chemistry offers a longer cycle life than TESLA lithium-ion batteries.  LiFePO4 batteries have a very constant discharge voltage, where each NiFePo4 cell voltage stays close to 3.2V during discharge, until the cell is exhausted. They allows the cell to deliver virtually full power until discharged, and simplifies or even eliminate the need for voltage regulation circuitry.

New lithium–sulphur battery technology is showing promise of highest performance-to-weight ratio, are being developed.

TESLA's Lithium-ion technology (is Not Iron) can pose unique safety hazards since the TESLA battery contain a flammable electrolyte and may need to be kept pressurised.   An expert notes "If a TESLA battery cell is charged too quickly, it can cause a short circuit, leading to explosions and fires". Because of these risks, testing standards are more stringent than those for acid-electrolyte batteries, requiring both a broader range of test conditions and additional battery-specific tests. There have been battery-related recalls by some companies, including the 2016 Samsung Galaxy Note-7 recall for lithium-ion battery fires.

Without prejudice, we highly recommend Lithium Iron Phosphate (LiFePo4) and Nickel Iron (NiFe) batteries, as they are the Safest & Cost less per kW, where NiFePo4 have the lowest cost per kW of under $550kW, closely followed by NiFe that have a proven track record and last over 30+ years, with some lasting over 100yrs, NiFe batteries don't use Lead or Acid, they use a cheap & readily available Electrolyte composed of Potassium hydroxide and Lithium hydroxide, that is reported to last minimum 7~10+ years, and when the electrolyte need replacing it only cost 5% of the battery cost, electrolyte replacement refreshes the batteries for the next 10 years !

Nickel Iron (NiFe) battery Electrolyte:

  • Potassium hydroxide (1.2g/cm3) is an inorganic compound with the formula KOH, and is commonly called caustic potash.
  • Lithium hydroxide (20g/L) is an inorganic compound with the formula LiOH. It is a white hygroscopic crystalline material. It is soluble in water and slightly soluble in ethanol, and is available commercially in anhydrous form and as the monohydrate (LiOH.H2O), both of which are strong bases. It is the weakest base among the alkali metal hydroxides.

As a long term Investment, there are only a few battery types that provide long term reliability, in the following order, Nickel Iron batteries, NiCd batteries (download.pdf), and possibly the new Australian RedFlow bromide batteries(worlds smallest Flow battery), Tesla Powerwall-2 Lithium-ion batteries, all are able to be used for Residential & Commercial applications.

NEWS: In January 2018 an Australian company 1414° degrees introduced a "Molten Silicon Energy Storage System" (Not a battery).  This is a Commercial 10MWh Thermal Energy storage system (TESS). Currently there smallest unit is 10MWh system, with an approx. footprint size, of a 40' shipping container and twice as wide, only designed for Large scale applications (250+ homes), a 1414° 200MWh system is the size of a two story building, currently these storage systems are Not for households, however it is claimed that a 10~50kWh system, if developed will only require 70cm3 for the molten core of Silicon (Si).

Super Capacitors for Energy Storage:

Super Capacitors (imag-1 image-2) are the latest in Energy storage device, although a little expensive they make a great addition to any micro grid storage system, Super Capacitor can be wired in Parallel or in Series to produce various voltage up to 750v, a Super Capacitors banks is NOT a chemical battery as such, Super Capacitors can Instantly release the total energy stored, unlike a battery that have limited energy release!

So why would we use a Capacitor bank ?  Well, if say a Water Heater, Oven or equipment that requires high amps to start, then instead of placing the Initial High load on your battery bank, it simply first Draw this power from the Super Capacitor bank, eliminating the load on your batteries, thus extending the life of your batteries, and Super Capacitors Charge back-up in a matter of a few minutes, compared to batteries.

Charging Batteries & Super Capacity Storage:

Besides Solar, an auto-start 4~10kW silenced Diesel Generator is the easiest, cheapest ($600~$6'000) and quickest methods to instantly increase your power production, Gen-set with starter motors will be automatically started by the Hybrid inverter.

Remember: Whilst a diesel generators are operating, the Hybrid inverter's built-in battery Charge controller (1~120A) will also be charging your batteries or Super Capacitors, this way very little fuel is wasted, our generator can be programmed to automatically start & shut-down as required, be it for just a short time several times a day or to just operate long enough to simply charge the batteries to get you through until sunrise.

Can I use a Battery bank to load-shift ?

Yes, battery storage connected to the Grid allows households without Solar, to take advantage of cheap off-peak electricity prices. The idea is to charge the batteries during off-peak times, and then use the stored electricity during peak times. This is known as Load-Shifting – But it doesn't make much financial sense unless there is a substantial difference between the day and off-peak power rates.

All batteries can off-set whatever kW of electricity they store, for example, a premises with a 10kWh battery bank, consuming 10kWh day, can charge the batteries in approx. 4 hours @$0.28 to $1.12 per day using the inverters' 120A Battery Charge circuit (or power from a diesel generator can be used), so charging the batteries at off-peak rate of $0.07 c/kWh cost $0.28 per day. This gives a saving of $0.84 per day, or around $310 per year. As a NiFe battery bank & inverter costs around $6,000, unfortunately a $0.84 day  savings would give a payback period of 19 years, But that is not the point, as a 2kWh Solar array will reduce the period to under 7 years, and under 3 years if your Solar array is already paid for in power savings, and would be FREE thereafter!

Will battery storage become cheaper ?

Yes, the costs of battery used for energy storage have been falling at a rapid rate and forecasts are for this trend to continue as more and more households adopt them. For example, the cost of battery storage fell 14% every year on average between 2007 and 2016 and it's expected that prices will halve again within the next five years.

Simply looking at these battery types, it is easy to see the wholesale battery cost per *kW;

  1. 7.68 kWh Lithium iron phosphate (LiFePo4) batteries cost approx. $4'175 ÷ 5.2kWh =$545 per kW.
  2. 12.0 kWh Nickel iron (NiFe) batteries cost approx. $6'720 ÷ 12.0kWh =$560 per kW.
  3. 13.5 kWh Tesla Lithium-ion batteries cost approx. $8'800 ÷ 13.5kWh =$650 per kW.
  4. 10.0 kWh RedFlow Bromide batteries cost approx. $10'000 ÷ 10kWh =$1'000 per kW (Australian).

Clearly leaving LiFe & NiFe batteries well ahead of thee rest in price and proven reliability, with NiFe reported "as new" after 30+ years!

Solar panels are also getting cheaper, with a 75% drop in price over the past five years.

With the global market for solar panels and battery storage expected to grow ten-fold by 2020, the demand for battery systems like Nickel Iron (Non acid), RedFlow (Bromide) etc. should have flow-on effects on prices as economies of scale kick in.

* approximate figures.

 

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