利用能量收集進行電力接入控制

　　電源是一個關鍵的挑戰，適合訪問控制系統，如電子鎖。能夠從環境中提供這樣的設備提供更低的成本，更容易集成和配件，并有可能使整個系統更安全，消除了切割電源的脆弱性。本文著眼于使用能源收集和電源管理提供加密的無線接入控制系統，連接到互聯網的東西，特別側重于太陽能的能源選項。

　　在智能建筑的改造中，向門禁系統提供電源是一個關鍵的限制。運行電力電纜上下的門可能是復雜和昂貴的，系統架構師正在尋找不同的方式來提供智能系統的電源。成千上萬的門鎖經常更換電池是昂貴的，在許多情況下不切實際。

　　相反，能量收集提供了機會，沒有大量的布線提供電力，但有一些關鍵的考慮，無論是在安裝和系統設計，取決于能源。

　　The two most appropriate energy harvesting technologies for access control are solar and thermal power. While these generate relatively small amounts of current， this works for access control where small bursts of power are required to authorize access – usually through a wireless link or a card swipe - and release a lock from the captured and stored current. A wireless link back to a monitoring gateway also provides more security and can be used to trigger alarms if the power is cut or there are unauthorized attempts at entry. Using an energy harvesting approach with a wireless link eliminates the need for a costly cable infrastructure and simplifies the retrofitting of such systems.

　　For external doors， the difference in temperature can be harnessed by energy sources using the Peltier Effect. This makes use of the different electrical and thermal properties of metals so that a Peltier engine， such as the WPG-1 from Laird Technologies （Figure 1）， can be installed in a door or through a wall with one side warmer than the other. This then generates a current that can be used to charge a battery to power the access control system.