Gist for using NMeasure for surplus energy in atmosphere...

IiUnitTests.cs

using System.Collections.Generic;
using Xunit;
using static NMeasure.U;
using static NMeasure.Tests.IiUnits;

namespace NMeasure.Tests
{
    public class IIUnitsTests
    {
        public IIUnitsTests()
        {
            StandardUnitConfiguration.Use().Extend<IiUnitsDefinition>();           
        }

        [Theory, MemberData("TestSource")]
        public void SomeConversions(Unit first, Unit second, decimal input, decimal expected)
        {
            var m1 = input * first;
            m1.ConvertTo(second).Value.IsEqualTo(expected);
        }

        [Fact]
        public void SoWhatAboutTheSpeedOfLight()
        {
            var speedOfLight = PhysicalConstants.SpeedOfLight.ConvertTo(ShipLength / Heartbeat);
            speedOfLight.Value.IsEqualTo(100000m);
        }

        public static IEnumerable<object[]> TestSource()
        {
            yield return new object[] { ShipLength, Kilometer, 1m, 2.4640m };
            yield return new object[] { QMichron, Hour, 50m, 28.5388m }; 
        }
    }

    internal static class IiUnits
    {
        private static IUnitFactory _units;
        private static IUnitFactory UnitsFactory => _units ?? (_units = GetUnitFactory());

        public static readonly Unit ShipLength = UnitsFactory.CreateRootUnit("SL");
        public static readonly Unit MicroShipLength = UnitsFactory.CreateRootUnit("mSL");
        public static readonly Unit Heartbeat = UnitsFactory.CreateRootUnit("IH");
        public static readonly Unit Michron = UnitsFactory.CreateRootUnit("IMc");
        public static readonly Unit QMichron = UnitsFactory.CreateRootUnit("IQMc");
        public static readonly Unit GreatMichron = UnitsFactory.CreateRootUnit("IGMc");
        public static readonly Unit Period = UnitsFactory.CreateRootUnit("IP");
        public static readonly Unit ShipMass = UnitsFactory.CreateRootUnit("IM");
        public static readonly Unit SunMass = UnitsFactory.CreateRootUnit("ISM");

        public class IiUnitsDefinition : IUnitConfigurationExtension
        {
            public void Extend(UnitConfiguration c)
            {
                c.Unit(MicroShipLength)
                    .IsPhysicalUnit(_LENGTH)
                    .StartScale()
                    .To(ShipLength, 1000);
                c.Unit(Heartbeat)
                    .IsPhysicalUnit(_TIME)
                    .StartScale()
                    .To(Michron, 50)
                    .To(QMichron, 50)
                    .To(GreatMichron, 50)
                    .To(Period, 250);
                c.Unit(ShipMass)
                    .IsPhysicalUnit(_MASS)
                    .ConvertibleTo(SunMass, m => m / 10E+25m, m => m * 10E+25m);

                c[ShipLength].ConvertValueBased(Kilometer, v => v * 2.4640476m, v => v / 2.4640476m);
                c[Heartbeat].ConvertValueBased(Second, v => v * 0.821917808219178m, v => v / 0.821917808219178m);
                c[ShipMass].ConvertValueBased(Kilogram, v => v * 55402.15m, v => v / 55402.15m);
            }
        }
    }
}

Program.cs

using System;
using NMeasure;

using static NMeasure.U;
using static System.Math;

namespace UsinMB
{
    public class Program
    {
        public static void Main(string[] args)
        {
            StandardUnitConfiguration.Use();
            
            var rEarth = (6371 * Kilometer).ConvertTo(Meter);
            var rAir = (6373 * Kilometer).ConvertTo(Meter);
            var dAir = 1.225m * Kilogram / (Meter ^ 3);
            var Cv = 718 * Joule / (Kilogram * Kelvin);
            var tempIncrease = 2 * Kelvin;
            
            var volume = 4d / 3d * PI * ((rAir ^ 3) - (rEarth ^ 3));
            
            var surplusEnergy = (volume * dAir * Cv * tempIncrease).ConvertTo(GigaJoule);
            
            var annualEnergyInGJ = 3600d * 23536500d;
            
            Console.WriteLine(volume);
            Console.WriteLine(volume * dAir);
            Console.WriteLine(surplusEnergy);
            Console.WriteLine(Convert.ToDouble(surplusEnergy.Value) / annualEnergyInGJ);
            Console.ReadLine(); 
        }
    }
}

Formatted...

1'020'449'218'718'634'278.1 m^3 (1.020e+18)
1'250'050'292'930'326'990.67 kg (1.250e+18)
1'795'072'220'647.95 GJ (1.795e+12)
21.19