There is currently a lot of interest in energy harvesting and many components are on the market to help design. For example:

http://www.digikey.co.uk/product-highlights/uk/en/linear-technology-energy-harvesting-power-products/1600?WT.srch=1&mkwid=sNI8BgcTk&pcrid=71112007346&pkw=_cat%3Adigikey.co.uk&pmt=b&pdv=c

http://www.mide.com/products/volture/volture-vibration-energy-harvesting-products-catalog.php

The main technology areas are:

Solar:  (eg. has been used in watches for decades)

http://www.casio-intl.com/asia-mea/en/wat/standard/solar_power/

Vibration: (eg has also been used in watches for decades)

https://en.wikipedia.org/wiki/Automatic_watch and is now being used to generate micro-watts of power for all sorts of applications eg. wireless instrumentation on machines. http://www.ni.com/white-paper/12128/en/#toc3

Thermal: using temperature differences eg in a Thermo-electric module to generate electricity. eg http://www.abb.co.uk/cawp/seitp202/3f14873078d1db8ec1257a8a003f5d3b.aspx

Hope this helps

Regards

Paul

Let me try the second question: how battery gather renewable energy. 

Think about battery charging. There must be an independent power source for battery charging. That power source would be 'renewable energy'. So, conceptually, renewable energy sources would generate power, based on weather pattern. Then, that power can be used to charge battery. For PV, at night when there is no sun, it is not possible to charge battery. So, with PV, the only time a battery can charge is 'day-time'. Once the battery is full, you cannot charge it anymore even if there are additional power coming from PV, for example. Winds produce power at different times than PV. So, it is possible to charge battery at night using winds. How exactly the charging happens? it depends on how you set it up. This is going to be hot topics in the near future.

I hope I answered this question.

Regards,

Jeremy

The word "long-lasting" is misleading as it has to be quantified and validated by conducting accelerated life testing (ALT) or highly accelerated life testing (HALT) to examine the long-term reliability of the energy-harvesting wearable device.

i suggest that you do some literature search on the electroacive polymers (EAP) and piazoelectrics to understand how these materials harvest mechanical or vibrational energy from the environment or from the human body motion and covert them into electrical power. 

There are many failure modes of these energy harvesting devices such as current leakage, mechanical fatigue, thermal fatigue if exposed to cyclical high/ low temperatures, electric shortage, etc. Hence, it would be unrealistic to assume that these energy harvesting devices are long-lasting.

hope this helps.

In terms of the mechanisms for storing energy harvesting power, (and assuming you do not mean primary batteries) there are two main options, Batteries and super-capacitors. Battery life is based on the number of charge / discharge cycles and as Ingo said, life can be extended by limiting the depth of discharge, but only for Metal Hydride, Lithium and Lead acid (LA is not usually used for wearable applications). Ni Cadmium suffers from memory effect and so life is usually fixed at the manufacturing stage. Typical full discharge life is 500 cycles, this can be extended to over 3000 cycles for the latest Lithium Fe PO3 cells when using proper battery management techniques. Super-capacitors can be made with almost infinite life (1 M cycles) at body temperature but their energy storage capacity is relatively low, but improving all the time.

Low energy cells have a high internal resistance, so design of the electronics is important. If radio transmitting capability is needed (high current for infrequent time) a combined battery / capacitor system is used. The capacitor delivers the high power and the battery the long cyclic life.

Best Regards

Paul

http://eh-network.org/files/human_power.pdf

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