# Simulation of Electromagnetic Generator as Biomechanical Energy Harvester
## 1 Introduction  
One of the difficult challenges confronting human civilization today is energy demand, of which 70% to 80% is currently met through fossil fuels [1]. Current and emerging renewable and energy-harvesting systems such as solar, wind, hydroelectric, geothermal, ocean, wave, and hydrogen are opening new possibilities that offer viable alternatives in the quest for low-carbon and non-fossil fuel energy generation. Various research has been carried out to optimize the output of these technologies [2; 3; 4; 5]. Energy harvesting is another type of renewable energy source which has attracted researchers to pursue this in view of the global demand for portable electronic devices which continues to grow, and this has directly increased the need for wireless electrical power [6; 7; 8; 9; 10]. The expanding usage of portable electronic devices with small power requirements and wireless technology for modern medical devices has increased concern about the present technology of the conventional battery due to its limited lifespan and dimension. It has always been dominated by the battery size and capacity in determining the dimension, lifespan, and abilities of an electronic system [11]. These limitations have inspired many researchers to investigate energy harvesting as a potential energy source. Energy harvesting has gained research momentum in powering up electronic devices as it has the potential to generate power for a longer lifespan. These energy resource devices are constructed in a way to operate with very minimal maintenance time or almost nearly zero maintenance and are able to operate for a longer lifespan. Energy harvesting is commonly implemented as an additional energy resource to a main power source element to further optimize the system's reliability without power interruptions. Energy generation from solar light, radio frequency, mechanical motion, and temperature variation has been demonstrated to be a feasible replacement for the conventional batteries for low-power portable electronic devices such as wearable electronics and wireless sensor networks. Technology advancements in sensor-based energy harvesting systems and energy-efficient harvesting components have driven the growth of the global market. Figure 1 shows the global energy harvesting market value and projection. BCC Research through their survey report stated the global energy-harvesting system market was valued to be $323 million in 2011 [12], $880 million in 2014 [13], and $1.7 billion in the year 2018. This recorded more than 5 times of growth in 7 years. The global energy-harvesting system market value is projected to be more than double by the year 2023, which is $4.4 billion. This is equivalent to a compound annual growth rate (CAGR) of 20.2% from 2018 to 2023 [14]. Apart from energy generated from solar light, radio frequency, mechanical motion, and temperature changes, biomechanical energy harvesting is also another field with vast opportunities to replace conventional batteries. Through every single heartbeat to motion, human beings continuously dissipate energy. It's a norm for the human muscles to transform the calorie intake from food to mechanical work. The efficiency of this conversion is stated as 25% [15]. Many devices have been developed to utilize the human energy capacity in generating electrical power such as hand-crank generators, wind-up flashlights, and wristwatches [16]. The drawback of these conventional methods is the users must concentrate on the power-generating activities and this frequently results in short periods of focus. A longer duration of energy harvesting activity is only possible by harvesting the energy from everyday activities, and this will be possible by attaching the energy-harvesting device to any of the human's anatomical joints. One of the most suitable examples of this approach is the self-winding watch, where the arm movement was occupied to generate electrical power of 5 uW [17]. [PERSON] et al. [18; 19] investigated an energy harvester by using a backpack.