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Renewable Energy Generation Efficiency
Renewable energy, in general is not exceptionally efficient at harnessing the natural forces on earth. The free energy is the reason that the concept is persued at all. Since these systems are getting better, via technical innovation, this form of power generation has become cost effective. Since the energy is the only method of payoff, it is therefore critical to take care to be efficient behind the generation devices; be it homeowner, commercial building owner, or installer. This discussion will focus on the efficiency of the parts behind the renewable generation systems; solar, hydro or wind. The wire connections, terminals, the batteries, the charge controllers, and the inverters will all be scrutinized for efficiency.
AC and DC Wire Voltage Drop - Resistance
In general, any element resists electrical charge going through it to some degree. The elements that resist the least are called conductors, those that resist more vehemently are called insulators. With this in mind there is resistance in any conductor, and therefore a loss of electricity passing through it. In general 3% - 5% loss is acceptable when working with copper. Basic rule of thumb is use thicker wire until your loss is acceptable. Please use the information here to calculate your wire voltage drops and wire guage needs.
DC or Direct Current electricity has no wave form to it. The absence of this wave form reduces the propensity of movement of the current down single strand conductors due to their resistance. Also finely stranded copper wire is flexible at greater thicknesses. Stranded copper DC cabling should always be used for DC installations as it has less resistance, and will lead to a more efficient connection.
Click here for available DC connection wire
Battery Efficiency
Batteries are made up of roughly 2 parts, the acid or electrolyte, and the plates (anodes and cathodes) of lead. However, here is where the similarities stop and the niches begin. There are basically 3 chemistries of batteries available to renewable energy consumers. They are:
flooded - require maintenance & high amp tolerant (watering due to electrolysis)
gel - high amperage intolerant & maintenance free
agm - maintenance free, & high amp tolerant
Click here for a discussion regarding chemistries of batteries
Since all battery based renewable energy systems have inconsistant use and generation, they must be able to tolerate high amperage load and charging cycles, capturing the varying current. Should you choose agm or flooded batteries, you can purchase fewer as the higher amperage loads are acceptable and do not affect them. Should you choose gel batteries, you will need to buy more to keep the amperage per cell down to reasonable levels.
Now that we understand the battery types, lets discuss their efficiencies. All batteries under high amperage load / charging, are not perfect. In fact the loss of power due to ineffeciencies inside a battery have been thoroughly studied. Generally, the higher the current (amperage) through a battery at any voltage, the higher the loss. These studies were carried out by a German scientist, Peukert, and thus the Peukert Coefficient is name in honor of his work. Click here for more about the Peukert Coefficient. Basically the peukert coefficient is equal to the internal resistance of the battery. The higher the resistance, the less efficient the battery.
flooded batteries are 38% - 60% efficient depending on the amperage
Gel Cell batteries are 60% - 102% efficient depending on the amperage
AGM batteries are 85% - 102% efficient depending on the amperage
Losses can also be seen in the electrolysis. AGM and GEL batteries retard this process more than flooded lead acid batteries. This process uses water and energy to produce pure oxygen and hydrogen in the battery box. This hydrogen can be explosive if not properly vented.
Charger / Charge Controller Efficiency
The best chargers in the industry are roughly 95% efficient. However, many chargers range from 70% - 90% efficiency levels. The heat sinks in many chargers use some of this power and the rest is lost in the conversion or controller.
Inverter Efficiency
The best inverters in the industry are roughly 95% efficient. However, many inverters range from 70% - 90% efficiency levels. The heat sinks in many inverters use some of this power and the rest is lost in the conversion or controller.
Overall System Efficiency - Adding it All Up.
By now you should readily understand that no matter how much power you generate, the amount you can store and/or deliver is what really matters. The following examples illustrate the power difference and annual loss in dollar value due to inefficient components. It is easy to justify efficient components that are only mildly more expensive, they pay for themselves quickly.
Off Grid Home - 10kw Efficient
10kw * 6hrs * 300 days = 18000kwh/yr
Charger 95% Efficient
Inverter 95% Efficient
Wire In 97% Efficient
Wire Out 97% Efficient
Batteries 90% Efficient
18000 * .95 * .95 * .97 * .97 * .90
= 13,756 kw/yr Deliverable
13756kwh * $.07/kwh ~ $963
13756kwh * $.10kwh ~ $1375.60
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Off Grid Home - 10kw Inefficient
10kw * 6hrs * 300 days = 18000kwh/yr
Charger 90% Efficient
Inverter 90% Efficient
Wire In 95% Efficient
Wire Out 95% Efficient
Batteries 80% Efficient
18000 * .90 * .90 * .95 * .95 * .80
= 11,842 kwh/yr Deliverable
11,842kwh * $.07/kwh ~ $829
11,842kwh * $.10/kwh ~ $1184.20
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On Grid Warehouse - 10kw Efficient
10kw * 6hrs * 300 days = 18000kwh/yr
Inverter 95% Efficient
Wire In 97% Efficient
Wire Out 97% Efficient
18000 * .95 * .97 * .97
= 15,757 kwh/yr Deliverable
15757kwh * $.07/kwh ~ $1103
15757kwh * $.10kwh ~ $1575.70
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On Grid Warehouse - 10kw Inefficient
10kw * 6hrs * 300 days = 18000kwh/yr
Inverter 90% Efficient
Wire In 95% Efficient
Wire Out 95% Efficient
18000 * .90 * .95 * .95
= 14,620 kwh/yr Deliverable
14620kwh * $.07/kwh ~ $1023.43
14620kwh * $.10/kwh ~ $1462.00
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Renewable Energy Generation Main Page
Sun Xtender AGM Batteries for Permanent Renewable Energy Installations
Lifeline AGM Batteries for Mobile Renewable Energy Installations
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