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Check list solar lamps: overview of the minimum technical standards for solar lamps

A seemingly endless amount of solar lamps are available on the market. And newmodels are introduced almost daily. For those who want to realize a solar project, it is often not easy to find an adequate solar lamp in this flood of products.


Distinction of lamp types

A) Mini reading lamps
Most of the mini reading lamps available on the market are only of minimal brightness and are not suitable for replacing kerosene lamps.

B) Flashlights
Flashlights have high intensity focused light. They can also be helpful in particular workplaces in which lighting is required in a small space.

C) Portable room lights
As a type of mini solar home system, these lamps unite various qualities: they are capable of lighting a space and can also be used as a mobile flashlight. Their mobility also has advantages within a space. In contrast to standard solar home systems, they can be employed flexibly.

A and B are not suitable for replacing kerosene lamps due to their construction and lack of brightness. Therefore, they will not be considered in the following.


Brightness

Decisive for a lamp's usability is the brightness it emits (measured in lumen) with as little electricity consumption as possible (measured in watt).
A solar lamp intended as replacement for a kerosene lamp should have at least 60 lumen, while 100 lumen are recommended.
LED lamps can achieve a brightness of 100 lumen with an electricity consumption of only one watt. This high energy yield makes them interesting for solar products since LED lamps demand relatively small batteries and modules.


Burn time

Two things are to be differentiated in the burn time of a lamp:
a) Daily burn time: refers to normal daily use. By maintaining this time, the battery can be recharged completely. Minimum specification here: 4h/day
b) Autonomous time: refers to the maximum lighting time of a fully charged battery. Since a battery may be not fully charged in one day (for example, due to weather), professional systems have a battery storage surpassing normal use. Minimum specification: 2 x minimum burn time = 8 h


Battery

Unfortunately, there is no perfect battery type for solar lamps. Every type in use today has its particular advantages and disadvantages. These include, along with specific technical characteristics, also various levels of user friendliness.
Good quality NiMeH, Li Ion, and also GEL lead acid batteries can be used. Until now, NiMeH and GEL lead acid batteries have proven themselves most useful in practice. NiCd batteries are not recommended due to their memory effects and environmental burden.
Hopes are that battery research will soon find an optimal solution for energy storage.


Charge controller

To protect the battery against overcharging and deep-discharging, a charge controller is recommended.

Solar module

Integration or not?—Some solar lamps have an integrated solar module. This solution is not recommended for various reasons:

  • as a rule, the module is not large enough to reliably charge the battery;
  • the solar lamp has to be set out in the sun to charge, which is, harmful, in the first place, for the battery;
  • dust or rain could also considerably damage the lamps; and
  • charging outside of a closed space opens the way to theft.


Size

Savings are often made in the size of modules to reduce system costs. However, one should actually not calculate module size too closely. Module size should be oriented on the duration of sunshine during the rainy period. A region's annual average is thereby not appropriate for determining module size. As standard, one could say that for a battery with 2.8 Ah, the module should be no smaller than 1.5 Wp.


User information

The following features are recommended for designing user-friendly solar lamps:

  • battery charge status indicator;
  • indicator showing the charging of the lamp;
  • at least two levels of brightness; and
  • remote switch, to turn the lamp on and off conveniently should it be installed on the ceiling.


Robustness

Since the lamps can be used as both permanently installed units and mobile flashlights, robustness is an important aspect. Minimum standards are as follows:

  • drop test: the lamp must survive undamaged from a one-meter fall;
  • water and dust protection: minimum is IP41 standard; and
  • the module must additionally be equipped with a stable frame to prevent damages from bumps.


Guarantee (minimum standards)

Module
2 year product guarantee
20 year service guarantee

Lamps, including batteries: 
1 year minimum

When purchasing a lamp, it is crucial to make sure that the supplier is capable of fulfilling the manufacturer's guarantee services. This applies especially to the availability of replacement parts and the possibility to install them on location. This requirement should be listed explicitly in the purchase contract. (hs)

Source: sun-connect 4 | November 2010 (p. 3-4)