① Battery Guy now ② Doctor of Engineering -- Metallurgy and Ceramic Science @ Tokyo Institute of Technology (Institute of Science Tokyo since Oct. 01, 2024) *The ultimate goal was the photo-induced B-E Condensation.
Hydro, 9.6%; Solar/Wind/Geothermal, 3.1% -> 12.7% in total.
Nuclear, 7.1%.
Because of the depopulation and the use of highly energy-efficient air conditioner, refrigerator, LED lighting system etc., the electric-power consumption in Japan is expected to be decreased down to 726.8 TWh/yr (-31.2%) in 2050. Then, fossil-fuel-fed power would be decreased to 55.1% and renewables would be increased to 38.9% just by stopping old LNG-fed and coal-fed fire power plant. For example,
As described later, the breakdown would become improved by power-saving technologies. Then, fossil-fuel-fed power would be decreased to 46.9% and renewables would be increased to 39.9%. For example,
This can take place because of Joule-Thomson effect.
(∂T/∂P)subH > 0 at a lower temperature (a working temperature) than the inversion temperature. In this temperature range, the thermodynamic gain via intermolecular attractive force is lost by adiabatic expansion (then, the potential energy becomes higher). Since the total energy must be kept constant (since it is the adiabatic expansion), the molecular kinetic energy is decreased. It means the temperature decreases.
(∂T/∂P)subH = 0 at the inversion temperature, at which Lennard-Jones intermolecular potential that simulates van der Waals force and London dispersion force becomes the minimum value.
(∂T/∂P)subH < 0 at a higher temperature than the inversion temperature. In this temperature range, the potential energy is limited by intermolecular repulsive force rather than intermolecular attractive force. Then, the adiabatic expansion results in the potential energy decrease. As already mentioned, the total energy must be kept constant, then, the molecular kinetic energy is increased (the temperature increased). This can be shown when hydrogen is supplied from the high-pressure tank: H2 & NH3 Combustion Technologies (& economy a lot) -- The Way to Become the "Full-Fledged" Energy for Solar & Wind.
(cf. 1) Heat pump is also used for hot water supply, known as EcoCute in Japan. Hot-water supply and heating system has also been available.
More energy-efficient hybrid hot water supply system (= instant gas hot water supply and heat pump), known as EcoOne, is available in Japan. Hot-water supply and heating system has also been available -- the hybrid can be used even in a cold-district, such as Hokkaido.
Conventional instant gas hot water supply system, known as EcoJyozu, is also energy-efficient, though.
(cf. 2) Underground heat-pump air-conditioning system: it reportedly decreases the annual electric-power consumption by 49%.
(a) For large-scale facility:
By the year of 2011, 4691 underground heat pump and heat pipe air conditioning system have been installed: annual electric-power consumption reduction of 49% has been reported. It reportedly costed ￥250,000/kW-￥600,000/kW (closed-loop heat pump or heat pipe) or ￥100,000/kW-￥300,000/kW (open-loop heat pump).
300 kW would be fine. Thus, it would cost ￥75,000,000-￥180,000,000.
Heat, Q in [J], is disposed to the lower-temperature heat bath, i.e., it is, in nature, distributed to limitless number of microscopic states or, at least, to a larger number of microscopic states in the heat bath than those of the system. This is called the second law of thermodynamics,
dS = dQ/T >= 0,
where T in [K] is the temperature and S in [J/K] is the entropy which is described as
S = k logΩ (the base is e, here),
where k is Boltzmann constant in [J/K], and
Ω = exp(S/k) = M!/(N!(M-N!)) = subM C subN,
where M is the number of microscopic states and N is the number of particles or quasi-particles that are distributed to the microscopic states.
From a microscopic view point,
Entropy, S, is the perfectly digitized quantity as mentioned above;
Internal energy, U (The first law of thermodynamics is described as dQ = dU + dw in the closed system, and dQ = dH + dw in the open system, where w is the work and H is the enthalpy.), is microscopically composed of molecular vibrations and rotations that are quantized, and three-dimensionally distributed molecular random-translation that is, sort of, digitized (listed in descending order of energy-level difference);
Pressure, P (w = PV, where V is the volume.), is generated by the translational momentum of molecule, thus, sort of, digitized.
Temperature, T, can be described as T = (2/3)(mv^2/2)(1/k) where mv^2/2 is the kinetic energy of a molecule. Therefore, temperature is, sort of, digitized.
Heat, Q, is fundamentally transfers via particle or quasi-particle motion, such as photon, electron, molecule, phonon etc. as measured in (1/2)kT (for the photon, hν, where the h is Planck constant in [J s = J Hz^-1]).
(2) Heat transfer
The entropy difference, ΔS, between the two macroscopic states, the final state and the initial state, can be calculated as follows:
(a) When T is constant (isothermal process),
ΔS = kN{log(Vf/Vi)} = -kN{log(Pf/Pi)},
where N is the mole number, Vf is the volume at the final state, and Vi is the volume at the initial state.
When considering 1 mol of gas, kN = R, where R is the universal gas constant, thus, the above equation becomes
ΔS = R{log(Vf/Vi)} = -R{log(Pf/Pi)}.
(b) When V is constant (constant volume process),
ΔS = Cv{log(Tf/Ti)} = Cv{log(Pf/Pi)},
where Cv is the specific heat capacity at a constant volume.
(c) In addition, when P is constant (constant pressure process),
ΔS = Cp{log(Tf/Ti)} = Cp{log(Vf/Vi)},
where Cp is the specific heat capacity at a constant pressure.
(d) Adiabatic process.
We can only partially achieve ΔS = 0 via an adiabatic process that takes place within a practically enough short time, i.e., before it dissipates.
(3) State Function
Entropy, S is the state function, meaning entropy does not depend on the path of the change (⇔ totally differentiable).
Internal energy, U, and pressure, P, are also the state functions.
Temperature, T, and volume, V, are also the state functions.
In contrast, heat, Q, and work in thermodynamics, W = PV, are not the state functions. Thus, the product, T,low ΔS, is convenient in order to calculate the required heat dissipation or wasted heat. Or, the sum of dQn (n = 1, 2, 3, …) for each path must be calculated.
(4) Heat is dissipated in three ways: (a) thermal radiation, (b) thermal conduction, and (c) convection.
Although the heat is destined to be dissipated from a viewpoint of thermodynamics, we need to use the heat in an effective manner by reducing the waste heat dissipated in three ways.
(a) Thermal radiation
Heat transfers via thermal radiation according to the equation,
Erad = εσ(Th^4 - Tl^4),
where Erad is the heat flux in W m^-2, where ε is the emissivity (0 <= ε <= 1), σ is the Stefan-Boltzmann constant in W m^-2 K^-4, Th is the temperature of the higher-temperature matter in K, and Tl is the temperature of the lower-temperature matter in K.
In order to decrease electric-power consumption, the heat penetration through the window glass must be suppressed.
The heat outflow through the window amounts 58% in winter, and the heat penetration through the window amounts 73% in summer. Thus, we usually lower the blind in the office for the heat-insulation.
However, (1) the infrared permeability reduction through the window, which is due to the reflection via plasmon resonance in the metal thin film (Plasma resonance: electron plasma oscillation in the metal. At the short-wavelength limit, the inter-band transition takes place, which is about 500 nm for Au (5d), 300 nm for Ag (4d), 600 nm for Cu (3d), and 250 nm for Al (d-electron free), resulting in the decrease in the reflection.) and (2) the suppression of convective heat transfer by using double window structure -- the latter is a main subject of the next topic, can decrease the heat outflow and the heat penetration through the window without sacrificing natural lighting, then, the electric-power consumption both via air conditioning and lighting can be decreased, e.g., 15.8% and ～8% (23.8% in total), respectively (air conditioning in winter, 0.48 x 0.58 x (0.50/0.88) = 0.158; lighting, 0.24 x 0.33 = 0.08 when assuming 33% of electric-power is consumed during the day -- optical duct system is also useful in order to decrease the electric-power consumption via lighting).
In order to decrease electric-power consumption, the heat penetration through the wall must be suppressed, as well.
The heat outflow through the wall amounts 15% in winter, and the heat penetration through the window amounts 7% in summer.
(c) Heat transfer from the solid to the fluid via convection (the roof and the outer wall are usually surrounded by air)
Heat transfers via thermal conduction according to the equation,
Econ = (λ/d)(Th - Tl),
where Econ is the heat flux in W m-2, λ is the heat conductivity in W m^-1 K^-1 (= W m m^-2 K^-1), d is the length (in meter, m) of the matter through the which heat transfers.
Heat also transfers from the solid to the fluid according to the equation,
Etra = h(Th - Tl),
where Etra is the heat flux in W m^-2, h is the heat transfer coefficient in W m^-2 K^-1.
Heat transmission coefficient in total, Utot, is calculated as follows:
Utot = 1/(Σ 1/(λi/di) + Σ 1/hi),
where i = 1, 2, 3, ...
As the simplest model, Utot can be
Utot = 1/(1/h1 + 1/(λ2/d2)) + 1/h3),
where h1 is the heat transfer coefficient at the low-temperature side, λ2 and d2 are the heat conductivity and the thickness of the heat conductor such as a wall, and h3 is the heat transfer coefficient at the high-temperature side.
In addition, Erad,2-to-1 and Erad,2-to-3 must be considered at least.
Without forced convection, there can be a thin stagnant layer at the interfaces 1-2 and 2-3, where the heat conduction takes place: this is usually experimentally included in the heat transfer coefficient.
In order to decrease electric-power consumption, the heat penetration through the roof and the wall must be suppressed.
The heat outflow in winter through the roof, the outer wall, and the floor can amount, e.g., 5%, 15%, and 7%, respectively, and the heat penetrationin summer through them can amount, e.g., 11%, 7%, and 3%, respectively.
The thermal conductivity of the concrete is about 1.6 W m^-1 K^-1. By using an appropriate thermal insulator having a low thermal conductivity or a low heat transmission coefficient, such as glass wool (0.033-0.050 W m^-1 K^-1) and urethan foam (0.023-0.040 W m^-1 K^-1), the heat loss can be minimized. Then, the electric-power consumption via air conditioning can be decreased to some extent. Note that the heat transmission coefficient of air is, e.g., only 12 W m^-2 K^-1 at 300 K (= 0.012 W m^-1 K^-1 at 1 mm).
We do not want to live in a PVC-wrapped house. By using the infrared reflector, in which the reflection is based on plasmon resonance, covering the thermal insulators' surface, you can effectively insulate the heat. The 7.5% (0.48 x 0.58 x 0.27 = 0.075) of electric-power consumption decrease is theoretically possible: 23.8 + 7.5 = 31.3% in a cumulative manner.
(5) Heat exchange
In order to decrease electric-power consumption, the heat dissipation via ventilation must be suppressed.
The heat outflow through the ventilation amounts 15% in winter, and the heat penetration through the ventilation amounts 6% in summer.
We need oxygen, thus, ventilation. Heat-exchangers have been available for ventilation: あたたか族®.
Electric-power consumption decrease: 4.2% (0.48 x 0.58 x 0.15 = 0.042), 31.3 + 4.2 = 35.5% in a cumulative manner.
(a) With a larger surface area, the more heat can be exchanged.
Heat, q in W, is exchanged through the exchanger according to the equation,
q = Utot A ΔT,
where A is the surface area.
(b) With the higher flow rate of the working fluid, the more heat can be exchanged.
Heat, q, is also described as
q＝(V/t) c ρ ΔT,
where (V/t) in L s^-1 is the flow rate per unit time, c in J kg^-1 K^-1 is the specific heat, ρ in kg L^-1 is the density.
IV. Summary
The electric power generation of Japan is about 1,000 TWh/yr.
Private business sector consumes 37.8% of electric-power; private households, 31.7%; industrial, 30.5%.
The latest energy-saving equipment, can decrease electric-power consumption: refrigerator, 10%; LED lighting system, 5%; air conditioner, 2-4% etc. Thus, 7-9% of 37.8% (2.6-3.4% of the total consumption) and 17-19% of 31.7% (5.4-6.0% of the total consumption) can be decreased. 8.0-9.4% in total.
In the private business sector, e.g., the 48% and 24% of purchased electric-power are used for air conditioning and lighting in the office, respectively.
For example, (35.5+X)% of electric-power consumption can be decreased in the private business sector (= 13.4% of the total) via (1) infrared permeability reduction through the window, (2) the suppression of convective heat transfer by using double window structure, (3) heat insulating wall, and (4) ventilation with heat exchanger. 21.4-22.8% in total.
It has been expected that the population in Japan is going to decrease to 0.9708 * 10^8 in 2050 (-23.7%). Therefore, the electric-power consumption can become between 0.763 * 0.786 = 0.60 and 0.763 * 0.772 = 0.59. Decrease by 40-41% in the best scenario in 2050 -- green power would reach 39.9% just by stopping old LNG-fed and coal-fed fire power plant.
The success of HEVs is due to the decoupling. This concept can also be applied to power generation/storage/consumption, e.g., (i) capacitor bank for several to several dozens seconds, (ii) battery bank for several to several dozens minutes (the cost must be considered), (iii) hydrogen for several to several dozens hours (the boil-off must be considered), and (iv) ammonia for several to several dozens days.
The backup for renewables via fire-power would be required. Then, H2 and NH3 would be required more and more, instead of fossil fuels. The challenging issue is the cost: (i) H2 at ¥13.3/Nm^3 is equivalent to LNG at $10/MMBtu (¥8.7/kWh); NH3 at ¥20.2/Nm^3 is equivalent to LNG at $10/MMBtu (¥8.7/kWh).
By the way, the CO2 emission from Japan is only 3.2% of the global CO2 emission; thus, this matter should be discussed only from the economic viewpoint in Japan.
