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Summary
Across
this month's survey of 499 prices from 31 online retailers,
there were 27 price increases offset by 15 price decreases.
This contrasts with last month where there were 47 price
increases and 18 price decreases. Over
the last year, only in the March 2008 result did the number
price decrease exceed the increases.
Unlike
like the methodology for the solar module price index computation
(which separates out European based dealers from United
States dealers, the Battery index pools all the prices in
the survey and simply translates them in to either dollars
or euros (no matter what the originating currency is).
The
European index is simply the (worldwide survey) dollar index
as represented in euros. It does not represent "European
only" retailers.
In
the past month, the dollar strengthened modestly against
the euro. The overall euro index is up to €1.30
per output watt hour.
Unlike solar modules and inverters, batteries are a mature
technology and a product that is used in volume outside
the solar energy industry. Consequently, the opportunity
for major cost breakthroughs over the medium term is limited.
Batteries are used in the substantial off-grid solar markets,
but also in on-grid markets, where the customer requires
power even during periods that the electricity grid is down.
Batteries can account for around 15% of the cost of an installed
Solar Energy System.
While there are many more Battery Manufacturers (click
here to see listing) than Solar Cell Manufacturers,
the market is segmented both by Battery Technology and location.
Not all Battery Manufacturers serve the solar electric market.
Lead acid batteries can be categorized in different ways.
The first is by the form of construction of the electrode
plates, either as flat plates or tubes. Tubular plates offer
larger capacities. The lead used to make the plates is generally
alloyed with elements like antimony, selenium, arsenic,
calcium or tin to optimize battery characteristics.
The second is according to whether the battery is vented
or valve-regulated. In a vented battery, gas produced during
over-charging can escape, but the lost water has to be replaced.
Valve
regulated lead acid cells (VRLA) are sealed and the gas
produced during over-charging at the positive electrode
is re-converted to water at the negative electrode. A valve
regulates excessive pressure build up.
There are two types of VRLA batteries. In one, the acid
is absorbed in a glass mat (AGM) and in the other, the acid
is immobilized in a gel. VRLA batteries, especially AGM
types are more temperature sensitive than vented batteries
and should be operated at temperatures close to 20°C for
long life.
The high weight to price ratio means that where possible
companies minimize transportation of batteries. Therefore,
it is typical, for example, for a European Manufacturer
to mainly serve European markets.
The Price Index is based upon "Price per watt hour"
rating. This is not a perfect measure, since technology
choice and other technical factors are relevant. However,
the consistent approach in the Index provides an accurate
guide on the direction and magnitude of changes.
The
Index calculation is based upon the aggregate of all the
prices divided by the aggregate output watts at 20 Amp hours.
Consequently a price per watt hour at 20 amp hours of discharge
is the result.
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